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