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