{"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\n\u003cscript\u003e\n window.katexOptions \u003d {\n delimiters: [\n {left: \u0027$$$$$$\u0027, right: \u0027$$$$$$\u0027, display: true},\n {left: \u0027$$$\u0027, right: \u0027$$$\u0027, display: false},\n {left: \u0027$$\u0027, right: \u0027$$\u0027, display: true},\n {left: \u0027$\u0027, right: \u0027$\u0027, display: false}\n ]\n };\n\u003c/script\u003e\n","sections":[{"title":"","value":{"format":"HTML","content":"子序列的意义是可以通过删除给定字符串的任意个字符获得的新字符串(0个或者全部也是合法的)\n例如,对于字符串“ abaca”,以下字符串是子序列:“ abaca”,“ aba”,“ aaa”,“ a”和“”(空字符串)。 但是以下字符串不是子序列:“ aabaca”,“ cb”和“ bcaa”。\n\n你将得到一个由n个小写字母组成的字符串s。\n\n在一次操作中,你可以获取给定字符串的任何子序列t并将其添加到集合S中。集合S不能包含重复项。 此移动成本n− |t|,其中|t| 是添加的子序列的长度(即,代价等于删除的字符的数量)。\n\n你需要找到最小的成本以获取一个大小为k的集合S,如果不能则输出-1;"}},{"title":"Input","value":{"format":"HTML","content":"第一行包含两个数字n和 k(1 ≤n ≤100, 1 ≤ k ≤ 1e12) — 分别表示字符串长度长度和集合的大小\n第二行输入一个长度为n的字符s"}},{"title":"Output","value":{"format":"HTML","content":"如果有解,输出获得集合S的最小代价,否则输出-1"}},{"title":"Examples","value":{"format":"HTML","content":"\u003cdiv class\u003d\"sample-test\"\u003e \n \u003cdiv class\u003d\"input\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e \n \u003cpre\u003e4 5\nasdf\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"output\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e \n \u003cpre\u003e4\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"input\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e \n \u003cpre\u003e5 6\naaaaa\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"output\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e \n \u003cpre\u003e15\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"input\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e \n \u003cpre\u003e5 7\naaaaa\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"output\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e \n \u003cpre\u003e-1\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"input\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e \n \u003cpre\u003e10 100\najihiushda\n\u003c/pre\u003e\n \u003c/div\u003e \n \u003cdiv class\u003d\"output\"\u003e \n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e \n \u003cpre\u003e233\n\u003c/pre\u003e\n \u003c/div\u003e\n\u003c/div\u003e"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003e第一个样例中S\u003d { \"\u003cspan class\u003d\"tex-font-style-tt\"\u003easdf\u003c/span\u003e\", \"\u003cspan class\u003d\"tex-font-style-tt\"\u003easd\u003c/span\u003e\", \"\u003cspan class\u003d\"tex-font-style-tt\"\u003eadf\u003c/span\u003e\", \"\u003cspan class\u003d\"tex-font-style-tt\"\u003easf\u003c/span\u003e\", \"\u003cspan class\u003d\"tex-font-style-tt\"\u003esdf\u003c/span\u003e\" }. S中第一个元素的花费为0 ,其余元素的花费是1,所以结果是4\u003c/p\u003e"}}]}