{"trustable":false,"prependHtml":"\u003cstyle type\u003d\u0027text/css\u0027\u003e\n .input, .output {\n border: 1px solid #888888;\n }\n .output {\n margin-bottom: 1em;\n position: relative;\n top: -1px;\n }\n .output pre, .input pre {\n background-color: #EFEFEF;\n line-height: 1.25em;\n margin: 0;\n padding: 0.25em;\n }\n \u003c/style\u003e\n \u003clink rel\u003d\"stylesheet\" href\u003d\"//codeforces.org/s/96598/css/problem-statement.css\" type\u003d\"text/css\" /\u003e\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript type\u003d\"text/javascript\" async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS_HTML-full\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"\u003cp\u003eYou are a secret agent tasked with intercepting a message between two spies. The message has been encrypted using a mysterious function f that takes two strings s1 and s2, both of the same length and consisting only of lowercase English letters.The output of the function f is another string of the same length. The i-th character of the output is equal to the minimum of the i-th character of s1 and the i-th character of s2.\u003c/p\u003e\n\n\u003cp\u003eFor example, \u003cstrong\u003ef(\"bc\", \"cb\")\u003c/strong\u003e \u003d \u003cstrong\u003e\"bb\"\u003c/strong\u003e, and \u003cstrong\u003ef(\"nywyl\", \"yizey\")\u003c/strong\u003e \u003d \u003cstrong\u003e\"niwel\"\u003c/strong\u003e.\u003c/p\u003e\n\n\u003cp\u003eYou managed to intercept two strings, \u003cstrong\u003ea\u003c/strong\u003e and \u003cstrong\u003eb\u003c/strong\u003e, of the same length, which are believed to be the input and output of the function \u003cstrong\u003ef\u003c/strong\u003e. Your task is to find any string \u003cstrong\u003ec\u003c/strong\u003e such that \u003cstrong\u003ef(a, c) \u003d b\u003c/strong\u003e, or report that no such string \u003cstrong\u003ec\u003c/strong\u003e exists by outputting -1.\u003c/p\u003e\n\nYou know that time is of the essence as the message contains critical information that could potentially compromise national security. Can you decipher the message by finding the correct string \u003cstrong\u003ec\u003c/strong\u003e that will allow you to retrieve the original message?\n"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003eThe first line of input contains the string \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ea\u003c/i\u003e\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eThe second line of input contains the string \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eb\u003c/i\u003e\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eBoth \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ea\u003c/i\u003e\u003c/span\u003e and \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eb\u003c/i\u003e\u003c/span\u003e consist only of lowercase English letters, \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ea\u003c/i\u003e\u003c/span\u003e and \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eb\u003c/i\u003e\u003c/span\u003e have same length and this length is between \u003cspan class\u003d\"tex-span\"\u003e1\u003c/span\u003e and \u003cspan class\u003d\"tex-span\"\u003e100\u003c/span\u003e.\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003eIf there is no string \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ec\u003c/i\u003e\u003c/span\u003e such that \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ef\u003c/i\u003e(\u003ci\u003ea\u003c/i\u003e, \u003ci\u003ec\u003c/i\u003e) \u003d \u003ci\u003eb\u003c/i\u003e\u003c/span\u003e, print \u003cspan class\u003d\"tex-font-style-tt\"\u003e-1\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eOtherwise, print a string \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ec\u003c/i\u003e\u003c/span\u003e such that \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ef\u003c/i\u003e(\u003ci\u003ea\u003c/i\u003e, \u003ci\u003ec\u003c/i\u003e) \u003d \u003ci\u003eb\u003c/i\u003e\u003c/span\u003e. If there are multiple possible answers, print any of them. The string \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ec\u003c/i\u003e\u003c/span\u003e should be the same length as \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ea\u003c/i\u003e\u003c/span\u003e and \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eb\u003c/i\u003e\u003c/span\u003e and consist only of lowercase English letters.\u003c/p\u003e"}},{"title":"Sample 1","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003eab\naa\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003eba\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Sample 2","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003enzwzl\nniwel\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003exiyez\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Sample 3","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003eab\nba\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e-1\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003eThe first case is from the statement.\u003c/p\u003e\n\u003cp\u003eAnother solution for the second case is \"\u003cspan class\u003d\"tex-font-style-tt\"\u003eyiyey\u003c/span\u003e\"\u003c/p\u003e\n\u003cp\u003eThere is no solution for the third case. That is, there is no \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ez\u003c/i\u003e\u003c/span\u003e such that \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ef\u003c/i\u003e(\u003c/span\u003e\"\u003cspan class\u003d\"tex-font-style-tt\"\u003eab\u003c/span\u003e\", \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ez\u003c/i\u003e) \u003d \u003c/span\u003e \"\u003cspan class\u003d\"tex-font-style-tt\"\u003eba\u003c/span\u003e\".\u003c/p\u003e"}}]}