#include <bits/stdc++.h>
using namespace std;
void run() {
  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 ||
      a + b + d == c || a + c + d == b || b + c + d == a)
    puts("YES");
  else
    puts("NO");
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  run();
  return 0;
}
