import core.bitop;
import std.algorithm;
import std.array;
import std.ascii;
import std.container;
import std.conv;
import std.format;
import std.math;
import std.range;
import std.stdio;
import std.string;
import std.typecons;

void main()
{
  auto v = readln.chomp.split.map!(to!int);
  int n = v.front;
  int m = v.back;
  alias A = Tuple!(int, "to", int, "idx");
  auto adj = new A[][](n);
  A tekito;
  foreach (i; 0..m) {
    auto s = readln.chomp.split.map!(to!int);
    int a = s.front;
    int b = s.back;
    adj[a] ~= A(b, i);
    adj[b] ~= A(a, i);
    tekito = adj[b].back;
  }
  bool[] done = new bool[](m);
  int[] list = [tekito.to];
  int[] queue = [tekito.to];
  while (queue.length) {
    int node = queue.front;
    queue = queue[1..$];
    foreach (next; adj[node]) {
      if (done[next.idx]) {
        continue;
      }
      done[next.idx] = true;
      list ~= next.to;
      queue ~= next.to;
    }
  }
  auto cnt = adj.map!(a => a.length).filter!(a => a % 2 == 1).count;
  stderr.writeln = cnt;
  stderr.writeln = done;
  bool ans = !done.any!(a => !a) && (cnt == 0 || cnt == 2);
  enum R = ["NO", "YES"];
  R[ans].writeln;
}