{"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\u003eGiven an undirected graph, your task is to choose a direction for each edge so that in the resulting directed graph each node has an even outdegree. The outdegree of a node is the number of edges coming out of that node.\u003c/p\u003e\n\u003ch1 id\u003d\"input\"\u003eInput\u003c/h1\u003e\n\u003cp\u003eThe first input line has two integers \u003cspan class\u003d\"math inline\"\u003e$ n $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ m $\u003c/span\u003e: the number of nodes and edges. The nodes are numbered \u003cspan class\u003d\"math inline\"\u003e$ 1,2,\\dots,n $\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eAfter this, there are \u003cspan class\u003d\"math inline\"\u003e$ m $\u003c/span\u003e lines describing the edges. Each line has two integers \u003cspan class\u003d\"math inline\"\u003e$ a $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ b $\u003c/span\u003e: there is an edge between nodes \u003cspan class\u003d\"math inline\"\u003e$ a $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ b $\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eYou may assume that the graph is simple, i.e., there is at most one edge between any two nodes and every edge connects two distinct nodes.\u003c/p\u003e\n\u003ch1 id\u003d\"output\"\u003eOutput\u003c/h1\u003e\n\u003cp\u003ePrint \u003cspan class\u003d\"math inline\"\u003e$ m $\u003c/span\u003e lines describing the directions of the edges. Each line has two integers \u003cspan class\u003d\"math inline\"\u003e$ a $\u003c/span\u003e and \u003cspan class\u003d\"math inline\"\u003e$ b $\u003c/span\u003e: there is an edge from node \u003cspan class\u003d\"math inline\"\u003e$ a $\u003c/span\u003e to node \u003cspan class\u003d\"math inline\"\u003e$ b $\u003c/span\u003e. You can print any valid solution.\u003c/p\u003e\n\u003cp\u003eIf there are no solutions, only print \"IMPOSSIBLE\".\u003c/p\u003e\n\u003ch1 id\u003d\"constraints\"\u003eConstraints\u003c/h1\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cspan class\u003d\"math inline\"\u003e$ 1 \\le n \\le 10^5 $\u003c/span\u003e\u003c/li\u003e\n\u003cli\u003e\u003cspan class\u003d\"math inline\"\u003e$ 1 \\le m \\le 2 \\cdot 10^5 $\u003c/span\u003e\u003c/li\u003e\n\u003cli\u003e\u003cspan class\u003d\"math inline\"\u003e$ 1 \\le a,b \\le n $\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\u003e4 4\n1 2\n2 3\n3 4\n1 4\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e1 2\n3 2\n3 4\n1 4\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e "}}]}