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