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