#include <bits/stdc++.h>
using namespace std;
int v[5];
int main() {
  cin >> v[1] >> v[2] >> v[3] >> v[4];
  sort(v + 1, v + 5);
  if (v[1] + v[4] == v[2] + v[3] || v[1] + v[2] + v[3] == v[4])
    return cout << "YES\n", 0;
  cout << "NO\n";
  return 0;
}
