#include <stdio.h>

int main () {
  int n = 0;
  int m = 0;
  int a = 0;
  int b = 0;
  
  int res = 0;
  
  int e[100][100] = {};
  int is_ng = 0;
  
  res = scanf("%d", &n);
  res = scanf("%d", &m);
  for (int i = 0; i < m; i++) {
    res = scanf("%d", &a);
    res = scanf("%d", &b);
    a--;
    b--;
    e[a][b] = 1;
    e[b][a] = 1;
  }
  
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < i; j++) {
      for (int k = 0; k < j; k++) {
        is_ng += e[i][j]*e[j][k]*e[k][i];
      }
    }
  }
  
  if (is_ng > 0) {
    printf("No\n");
  } else {
    printf("Yes\n");
  }
  
  return 0;
}