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