#include <bits/stdc++.h>
using namespace std;
double x[4], y[4];
double ab, bc, cd, da, ac, bd;
double len(double x1, double y1, double x2, double y2) {
  return sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
}
double square(double a, double b, double c) {
  double s = (a + b + c) / 2.0;
  return sqrt(s * (s - a) * (s - b) * (s - c));
}
int main(void) {
  while (~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", x, y, x + 1, y + 1, x + 2,
                y + 2, x + 3, y + 3)) {
    ab = len(x[0], y[0], x[1], y[1]);
    bc = len(x[1], y[1], x[2], y[2]);
    cd = len(x[2], y[2], x[3], y[3]);
    da = len(x[3], y[3], x[1], y[1]);
    ac = len(x[0], y[0], x[2], y[2]);
    bd = len(x[3], y[3], x[1], y[1]);
    double s1, s2, s3, s4;
    s1 = square(ab, bd, da);
    s2 = square(cd, bd, bc);
    s3 = square(ac, cd, da);
    s4 = square(ab, bc, ac);
    double comp1;
    comp1 = (s1 + s2) + (s3 + s4);
    double mmax = max(max(s1, s2), max(s3, s4));
    if (fabs(mmax * 2.0 - comp1) > 0.001)
      puts("YES");
    else
      puts("NO");
  }
  return 0;
}
