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