#include <bits/stdc++.h>
using namespace std;
int main() {
  char e;
  double xa, ya, xb, yb, xc, yc, xd, yd, a, b, c, d;
  while (cin >> xa) {
    cin >> e >> ya >> e >> xb >> e >> yb >> e >> xc >> e >> yc >> e >> xd >>
        e >> yd;
    a = (xb - xa) * (xc - xb) + (yb - ya) * (yc - yb);
    b = (xc - xb) * (xd - xc) + (yc - yb) * (yd - yc);
    c = (xd - xc) * (xa - xd) + (yd - yc) * (ya - yd);
    d = (xa - xd) * (xb - xa) + (ya - yd) * (yb - ya);
    if (a * b < 0 || b * c < 0 || c * d < 0 || d * a < 0)
      cout << "NO" << endl;
    else
      cout << "YES" << endl;
  }
  return 0;
}
