#include <bits/stdc++.h>
using namespace std;
int main() {
  double xa, ya, xb, yb, xc, yc, xd, yd, s1, s2, s3, s4;
  while (scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &xa, &ya, &xb, &yb, &xc, &yc,
               &xd, &yd)) {
    s1 = abs((xc - xa) * (yb - ya) - (xb - xa) * (yc - ya));
    s2 = abs((xc - xa) * (yd - ya) - (xd - xa) * (yc - ya));
    s3 = abs((xb - xa) * (yd - ya) - (xd - xa) * (yb - ya));
    s4 = abs((xb - xc) * (yd - yc) - (xd - xc) * (yb - yc));
    if (s1 + s2 == s3 + s4) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
  return 0;
}
