#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  if (a + b == c + d || a + c == b + d || b + c == a + d || a == b + c + d ||
      b == a + c + d || c == a + b + d || d == a + b + c) {
    cout << "YES" << endl;
  } else
    cout << "NO" << endl;
  return 0;
}
