#include <bits/stdc++.h>
using namespace std;
double f(double x1, double y1, double x2, double y2, double x3, double y3,
         double x4, double y4) {
  return ((x1 - x2) * (y3 - y1) + (y1 - y2) * (x1 - x3)) *
         ((x1 - x2) * (y4 - y1) + (y1 - y2) * (x1 - x4));
}
int main() {
  int x[4], y[4];
  while (scanf("%f,%f,%f,%f,%f,%f,%f,%f", &x[0], &y[0], &x[1], &y[1], &x[2],
               &y[2], &x[3], &y[3]) != EOF) {
    if (f(x[0], y[0], x[1], y[1], x[2], y[2], x[3], y[3]) < 0 ||
        f(x[2], y[2], x[3], y[3], x[0], y[0], x[1], y[1]) < 0)
      cout << "NO" << endl;
    else
      cout << "YES" << endl;
  }
  return 0;
}
