#include <bits/stdc++.h>
using namespace std;
int a, b;
int main() {
  scanf("%d%d", &a, &b);
  if (a == 0 && b == 0) {
    printf("NO\n");
    return 0;
  }
  if (abs(a - b) > 1)
    printf("NO\n");
  else
    printf("YES\n");
  return 0;
}
