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