#include <bits/stdc++.h>
using namespace std;
int fx[] = {0, -1, 0, +1};
int fy[] = {-1, 0, +1, 0};
int main() {
  ios_base::sync_with_stdio(NULL);
  cin.tie(NULL);
  cout.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 ||
      b == a + c + d || c == a + b + d || d == a + b + c)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
