#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 || a + d == c + b || a + b + c == d ||
      a + c + d == b || b + c + d == a || c == a + b + d)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
