#include <bits/stdc++.h>
int abs(int a) { return a > 0 ? a : (-1) * (a); }
int main() {
  static int a, b;
  scanf("%d%d", &a, &b);
  if (a == 0 and b == 0) {
    printf("NO");
    return 0;
  }
  if (abs(a - b) <= 1) {
    printf("YES");
  } else {
    printf("NO");
  }
  return 0;
}
