{"trustable":true,"prependHtml":"\u003cstyle type\u003d\"text/css\"\u003e\n h1 { font-size: 1.2em; }\n\u003c/style\u003e\n","sections":[{"title":"","value":{"format":"HTML","content":"\n\u003cdiv class\u003d\"md\"\u003e\u003cp\u003eYour task is to count the number of sequences of length \u003cspan class\u003d\"math inline\"\u003e$ n $\u003c/span\u003e where each element is an integer between \u003cspan class\u003d\"math inline\"\u003e$ 1 \\dots k $\u003c/span\u003e and each integer between \u003cspan class\u003d\"math inline\"\u003e$ 1 \\dots k $\u003c/span\u003e appears at least once in the sequence.\u003c/p\u003e\n\u003cp\u003eFor example, when \u003cspan class\u003d\"math inline\"\u003e$ n\u003d6 $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ k\u003d4 $\u003c/span\u003e, some valid sequences are \u003cspan class\u003d\"math inline\"\u003e$ [1,3,1,4,3,2] $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ [2,2,1,3,4,2] $\u003c/span\u003e.\u003c/p\u003e\n\u003ch1 id\u003d\"input\"\u003eInput\u003c/h1\u003e\n\u003cp\u003eThe only input line has two integers \u003cspan class\u003d\"math inline\"\u003e$ n $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ k $\u003c/span\u003e.\u003c/p\u003e\n\u003ch1 id\u003d\"output\"\u003eOutput\u003c/h1\u003e\n\u003cp\u003ePrint one integer: the number of sequences modulo \u003cspan class\u003d\"math inline\"\u003e$ 10^9+7 $\u003c/span\u003e.\u003c/p\u003e\n\u003ch1 id\u003d\"constraints\"\u003eConstraints\u003c/h1\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cspan class\u003d\"math inline\"\u003e$ 1 \\le k \\le n \\le 10^6 $\u003c/span\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch1 id\u003d\"example\"\u003eExample\u003c/h1\u003e\n\u003ctable class\u003d\"vjudge_sample\"\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\u003e6 4\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e1560\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e "}}]}