#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  int d[4];
  int num, x, y;
  for (num = 0; num <= 3; num++) cin >> d[num];
  for (a = 0; a <= 2; a++) {
    for (c = 0; c <= 2 - a; c++) {
      if (d[c] > d[c + 1]) {
        x = d[c];
        d[c] = d[c + 1];
        d[c + 1] = x;
      }
    }
  }
  if (d[3] == d[1] + d[0] + d[2])
    cout << "yes" << endl;
  else if (d[3] + d[0] == d[1] + d[2])
    cout << "yes" << endl;
  else if (d[3] + d[1] == d[0] + d[2])
    cout << "yes" << endl;
  else if (d[3] + d[2] == d[1] + d[0])
    cout << "yes" << endl;
  else
    cout << "no" << endl;
  return 0;
}
