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