#include <bits/stdc++.h>
using namespace std;
int main() {
  int p, b, c, d;
  cin >> p >> b >> c >> d;
  if (p == b + c + d || p + b == c + d || b == p + c + d || c == p + b + d ||
      d == p + b + c || p + c == b + d || p + d == b + c)
    cout << "yes";
  else
    cout << "No";
}
