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

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  vector<int> a(4);
  cin >> a[0] >> a[1] >> a[2] >> a[3];
  sort(begin(a), end(a));
  vector<int> b(4);
  iota(begin(b), end(b), a[0]);
  if (a == b) {
    cout << "Yes\n";
  } else {
    cout << "No\n";
  }
}