#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c, d, e, f, g, h, j, k, i, l, m, n, o;
  cin >> a >> b >> c >> d;
  f = a + b;
  g = a + c;
  h = a + d;
  i = b + c;
  j = b + d;
  k = c + d;
  l = a + b + c;
  m = a + b + d;
  n = a + c + d;
  o = b + c + d;
  if (f == k || g == j || h == i || l == d || m == c || n == b || o == a) {
    cout << "YES";
  } else
    cout << "NO";
  return 0;
}
