#include <bits/stdc++.h>
using namespace std;

int main() {
  vector<int> V(4);
  for (int i = 0; i < 4; i++) cin >> V.at(i);
  sort(V.begin(), V.end());
  for (int i = 1; i < 4; i++) if (V.at(i) != V.at(i - 1) + 1) return cout << "No" << "\n", 0;
  cout << "Yes" << "\n";
}