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