#include <bits/stdc++.h>
int a, b, test, i, j;
using namespace std;
int main() {
  int ara[4];
  cin >> ara[0] >> ara[1] >> ara[2] >> ara[3];
  sort(ara, ara + 4);
  if (ara[0] + ara[3] == ara[1] + ara[2] || ara[3] == ara[0] + ara[1] + ara[2])
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
