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