import std.stdio, std.string, std.conv, std.algorithm; import std.range, std.array, std.math, std.typecons, std.container, core.bitop; void main() { int n, m; scan(n, m); auto deg = new int[](n); auto adj = new int[][](n, 0); foreach (i ; 0 .. m) { int ai, bi; scan(ai, bi); adj[ai] ~= bi; adj[bi] ~= ai; deg[ai] ^= 1; deg[bi] ^= 1; } auto visited = new bool[](n); void dfs(int u) { visited[u] = 1; foreach (v ; adj[u]) { if (!visited[v]) { dfs(v); } } } foreach (u ; 0 .. n) { if (!adj[u].empty) { dfs(u); break; } } foreach (u ; 0 .. n) { if (!visited[u] && !adj[u].empty) { writeln("NO"); return; } } deg.sort!"a > b"(); if (deg.startsWith([1, 1, 0]) || deg.startsWith([0])) { writeln("YES"); } else { writeln("NO"); } } void scan(T...)(ref T args) { string[] line = readln.split; foreach (ref arg; args) { arg = line.front.to!(typeof(arg)); line.popFront(); } assert(line.empty); } void fillAll(R, T)(ref R arr, T value) { static if (is(typeof(arr[] = value))) { arr[] = value; } else { foreach (ref e; arr) { fillAll(e, value); } } }