#include <bits/stdc++.h>
using namespace std;
double calcS(double x1, double y1, double x2, double y2, double x3, double y3) {
  double S, s, ab, bc, ca;
  ab = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  bc = sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3));
  ca = sqrt((x3 - x1) * (x3 - x1) + (y3 - y1) * (y3 - y1));
  s = 0.5 * (ab + bc + ca);
  S = sqrt(s * (s - ab) * (s - bc) * (s - ca));
  return S;
}
int main() {
  double x1, y1, x2, y2, x3, y3, x4, y4;
  char c;
  while (1) {
    cin >> x1 >> c >> y1 >> c >> x2 >> c >> y2 >> c >> x3 >> c >> y3 >> c >>
        x4 >> c >> y4;
    if (cin.eof()) break;
    if (calcS(x1, y1, x2, y2, x3, y3) + calcS(x1, y1, x4, y4, x3, y3) ==
        calcS(x2, y2, x3, y3, x4, y4) + calcS(x2, y2, x1, y1, x4, y4))
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
