#include <bits/stdc++.h>
using namespace std;
int main() {
  double x[4], y[4];
  double x1, y1, x2, y2, x3, y3;
  int i;
  while (scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &x[0], &y[0], &x[1], &y[1],
               &x[2], &y[2], &x[3], &y[3]) != EOF) {
    for (i = 0; i < 4; i++) {
      x1 = x[(i + 2) % 4] - x[i];
      y1 = y[(i + 2) % 4] - y[i];
      x2 = x[(i + 2) % 4] - x[(i + 3) % 4];
      y2 = y[(i + 2) % 4] - y[(i + 3) % 4];
      x3 = x[(i + 2) % 4] - x[(i + 1) % 4];
      y3 = y[(i + 2) % 4] - y[(i + 1) % 4];
      if ((x1 * x2 + y1 * y2) < 0 && (x1 * x3 + y1 * y3) < 0) {
        i = 10;
        break;
      }
    }
    if (i < 10)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
