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