#include <bits/stdc++.h>
using namespace std;
bool check(double X1, double Y1, double X2, double Y2, double X3, double Y3,
           double X4, double Y4) {
  return ((X1 - X2) * (Y3 - Y1) - (Y1 - Y2) * (X3 - X1)) *
             ((X1 - X2) * (Y4 - Y1) - (Y1 - Y2) * (X4 - X1)) >
         0.0;
}
void solve() {
  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))
    if (check(xa, ya, xc, yc, xb, yb, xd, yd) ||
        check(xb, yb, xd, yd, xa, ya, xc, yc)) {
      cout << "NO" << endl;
    } else {
      cout << "YES" << endl;
    }
}
int main() {
  solve();
  return (0);
}
