#include <bits/stdc++.h>
using namespace std;
long long a[5];
int main() {
  for (int i = 1; i <= 4; ++i) scanf("%I64d", &a[i]);
  sort(a + 1, a + 5);
  if (a[1] + a[4] == a[2] + a[3] || a[1] + a[3] == a[2] + a[4] ||
      a[1] + a[2] + a[3] == a[4])
    printf("YES\n");
  else
    printf("NO");
  return 0;
}
