#include <bits/stdc++.h>
using namespace std;
int line(double x1, double y1, double x2, double y2, double xp, double yp) {
  if (x1 != x2) {
    y1 = (y2 - y1) * (xp - x1) / (x2 - x1) + y1;
  }
  if (yp - y1 > 0)
    return 1;
  else
    return -1;
}
int main() {
  double xa, ya, xb, yb, xc, yc, xd, yd;
  while (scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &xa, &ya, &xb, &yb, &xc, &yc,
               &xd, &yd) != EOF) {
    int a, b, c, d;
    a = line(xb, yb, xd, yd, xa, ya);
    b = line(xa, ya, xc, yc, xb, yb);
    c = line(xb, yb, xd, yd, xc, yc);
    d = line(xa, ya, xc, yc, xd, yd);
    if (a + c == 0 && b + d == 0) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
  return 0;
}
