#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, j = 0, k = 0, l, p, n, m, a, s, t, c;
  cin >> n >> m;
  if (n == 0 && m == 0) {
    cout << "NO" << endl;
    return 0;
  }
  s = n + m;
  p = abs(m - n);
  a = s / 2;
  if (s % 2 == 0) {
    if (n == a && m == a)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  } else {
    if (p == 1)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
