{"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":"题目描述","value":{"format":"MD","content":"你正在学习单词,已知单词由n个字母组成,并且有m(\u0027a\u0027-\u0027z\u0027是前26个,\u0027A\u0027和\u0027Z\u0027是后26个)个不同种类的字母可选,除此之外,还有k个限制,比如给出限制为“ab”,代表a之后不能紧接着b,(注意:只是不能紧接,\"acb\"可以),请你编写程序求出你能学多少个不同的单词,答案对1e9+7取模\n"}},{"title":"输入","value":{"format":"MD","content":"第一行包含 $3$ 个整数 $n,m,k$ ,含义见题目描述;\n\n接下来 $k$ 行,每行包含一个长度为 $2$ 的字符串,字符串由小写字母和大写字母构成——字母\u0027a\u0027~\u0027z\u0027,\u0027A\u0027~\u0027Z\u0027 ;表示题目描述中的 $k$ 个限制。"}},{"title":"输出","value":{"format":"MD","content":"\n一个整数,表示有多少种不同的单词,答案对 $(10^9+7)$ 取模。"}},{"title":"数据规模","value":{"format":"MD","content":"\n$1\\leq n\\leq 10^{15},1\\leq m\\leq 52,0\\leq k\\leq m^2$。"}},{"title":"Examples","value":{"format":"MD","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\u003e3 3 2\u003cbr\u003eab\u003cbr\u003eba\u003cbr\u003e\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\u003e17\u003cbr\u003e\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\u003e3 3 0\u003cbr\u003e\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\u003e27\u003cbr\u003e\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\u003e2 1 1\u003cbr\u003eaa\u003cbr\u003e\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\u003e0\u003cbr\u003e\u003c/pre\u003e\n \u003c/div\u003e\n\u003c/div\u003e"}},{"title":"Note","value":{"format":"MD","content":""}}]}