{"trustable":true,"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$$\u0027, display: true},\n {left: \u0027$\u0027, right: \u0027$\u0027, display: false}\n ]\n };\n\u003c/script\u003e\n","sections":[{"title":"","value":{"format":"HTML","content":"\u003cp\u003eAquaMoon and Cirno are playing an interesting game with arrays. Cirno has prepared two arrays $$$a$$$ and $$$b$$$, both consist of $$$n$$$ non-negative integers. AquaMoon can perform the following operation an arbitrary number of times (possibly zero):\u003c/p\u003e\u003cul\u003e \u003cli\u003e She chooses two indices $$$i$$$ and $$$j$$$ ($$$1 \\le i, j \\le n$$$), then decreases the $$$i$$$-th element of array $$$a$$$ by $$$1$$$, and increases the $$$j$$$-th element of array $$$a$$$ by $$$1$$$. The resulting values at $$$i$$$-th and $$$j$$$-th index of array $$$a$$$ are $$$a_i - 1$$$ and $$$a_j + 1$$$, respectively. Each element of array $$$a$$$ \u003cspan class\u003d\"tex-font-style-bf\"\u003emust be non-negative after each operation\u003c/span\u003e. If $$$i \u003d j$$$ this operation doesn\u0027t change the array $$$a$$$. \u003c/li\u003e\u003c/ul\u003e\u003cp\u003eAquaMoon wants to make some operations to make arrays $$$a$$$ and $$$b$$$ equal. Two arrays $$$a$$$ and $$$b$$$ are considered equal if and only if $$$a_i \u003d b_i$$$ for all $$$1 \\leq i \\leq n$$$.\u003c/p\u003e\u003cp\u003eHelp AquaMoon to find a sequence of operations that will solve her problem or find, that it is impossible to make arrays $$$a$$$ and $$$b$$$ equal.\u003c/p\u003e\u003cp\u003ePlease note, that you \u003cspan class\u003d\"tex-font-style-bf\"\u003edon\u0027t have to minimize\u003c/span\u003e the number of operations.\u003c/p\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003eThe input consists of multiple test cases. The first line contains a single integer $$$t$$$ ($$$1 \\leq t \\leq 100$$$) — the number of test cases.\u003c/p\u003e\u003cp\u003eThe first line of each test case contains a single integer $$$n$$$ ($$$1 \\leq n \\leq 100$$$).\u003c/p\u003e\u003cp\u003eThe second line of each test case contains $$$n$$$ integers $$$a_1, a_2, \\dots, a_n$$$ ($$$0 \\leq a_i \\leq 100$$$). \u003cspan class\u003d\"tex-font-style-bf\"\u003eThe sum of all $$$a_i$$$ does not exceed $$$100$$$.\u003c/span\u003e\u003c/p\u003e\u003cp\u003eThe third line of each test case contains $$$n$$$ integers $$$b_1, b_2, \\dots, b_n$$$ ($$$0 \\leq b_i \\leq 100$$$). \u003cspan class\u003d\"tex-font-style-bf\"\u003eThe sum of all $$$b_i$$$ does not exceed $$$100$$$.\u003c/span\u003e\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003eFor each test case print \"\u003cspan class\u003d\"tex-font-style-tt\"\u003e-1\u003c/span\u003e\" on the only line if it is impossible to make two arrays equal with some sequence of operations.\u003c/p\u003e\u003cp\u003eOtherwise, print an integer $$$m$$$ ($$$0 \\leq m \\leq 100$$$) in the first line — the number of operations. Then print $$$m$$$ lines, each line consists of two integers $$$i$$$ and $$$j$$$ — the indices you choose for the operation.\u003c/p\u003e\u003cp\u003eIt can be proven that if it is possible to make two arrays equal with some sequence of operations, there exists a sequence with $$$m \\leq 100$$$.\u003c/p\u003e\u003cp\u003eIf there are multiple possible solutions, you can print any.\u003c/p\u003e"}},{"title":"Examples","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003e4\n4\n1 2 3 4\n3 1 2 4\n2\n1 3\n2 1\n1\n0\n0\n5\n4 3 2 1 0\n0 1 2 3 4\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e2\n2 1\n3 1\n-1\n0\n6\n1 4\n1 4\n1 5\n1 5\n2 5\n2 5\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003eIn the first example, we do the following operations:\u003c/p\u003e\u003cul\u003e \u003cli\u003e $$$i \u003d 2$$$, $$$j \u003d 1$$$: $$$[1, 2, 3, 4] \\rightarrow [2, 1, 3, 4]$$$; \u003c/li\u003e\u003cli\u003e $$$i \u003d 3$$$, $$$j \u003d 1$$$: $$$[2, 1, 3, 4] \\rightarrow [3, 1, 2, 4]$$$; \u003c/li\u003e\u003c/ul\u003e\u003cp\u003eIn the second example, it\u0027s impossible to make two arrays equal.\u003c/p\u003e"}}]}