#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, pp = 0;
  cin >> a >> b;
  if (a < b) {
    if (b - a == 0 || b - a == 1) pp = 1;
  } else if (a - b == 0 || a - b == 1)
    pp = 1;
  if (pp == 1 && (a != 0 || b != 0))
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
