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