#include <bits/stdc++.h>
using namespace std;
double dist(double x1, double y1, double x2, double y2) {
  return sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}
double deg(double a, double b, double c) {
  return acos((a * a + b * b - c * c) / (2 * a * b));
}
double calc_deg(double x1, double y1, double x2, double y2, double x3,
                double y3) {
  double x, y, z;
  x = dist(x1, y1, x2, y2);
  y = dist(x2, y2, x3, y3);
  z = dist(x3, y3, x1, y1);
  return deg(x, y, z);
}
int main() {
  double x1, y1, x2, y2, x3, y3, x4, y4;
  char c;
  while (cin >> x1 >> c >> y1 >> c >> x2 >> c >> y2 >> c >> x3 >> c >> y3 >>
         c >> x4 >> c >> y4) {
    double deg1, deg2, deg3, deg4;
    deg1 = calc_deg(x1, y1, x2, y2, x3, y3);
    deg2 = calc_deg(x2, y2, x3, y3, x4, y4);
    deg3 = calc_deg(x3, y3, x4, y4, x1, y1);
    deg4 = calc_deg(x4, y4, x1, y1, x2, y2);
    if (abs(deg1 + deg2 + deg3 + deg4 - 2 * M_PI) < 0.00001) {
      cout << "Yes" << endl;
    } else {
      cout << "No" << endl;
    }
  }
  return 0;
}
