#include <bits/stdc++.h>
int main() {
  int a, b, c, d;
  scanf("%d %d %d %d", &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 + d + c == b || b + c + d == a) {
    printf("YES");
  } else
    printf("NO");
}
