#include <bits/stdc++.h>
using namespace std;
int n, m;
int main() {
  while (scanf("%d %d", &n, &m) != EOF) {
    if (n == 0 && m == 0) {
      printf("NO\n");
      continue;
    }
    if (n < m) swap(n, m);
    if (n - m <= 1)
      printf("YES\n");
    else
      printf("NO\n");
  }
}
