#include <bits/stdc++.h>
using namespace std;
void solve() {
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  if ((a + b) == (c + d) || (a + c) == (b + d) || (a + d) == (b + c))
    cout << "YES";
  else if ((a + b + c) == d || (a + b + d) == c || (a + c + d) == b ||
           (b + c + d) == a)
    cout << "YES";
  else
    cout << "NO";
}
int main() {
  solve();
  return 0;
}
