#include <bits/stdc++.h>
float spase(float a, float b, float c) {
  return sqrt((a + b + c) * (b - a + c) * (a - b + c) * (a + b - c));
}
int main() {
  float a, b, c, d, e, f, g, h, AB, BC, CD, DA, AC, BD, abc, bcd, cda, dab;
  while (scanf("%f,%f,%f,%f,%f,%f,%f,%f", &a, &b, &c, &d, &e, &f, &g, &h) !=
         EOF) {
    AB = sqrt((a - c) * (a - c) + (b - d) * (b - d));
    BC = sqrt((c - e) * (c - e) + (d - f) * (d - f));
    CD = sqrt((e - g) * (e - g) + (f - h) * (f - h));
    DA = sqrt((g - a) * (g - a) + (h - b) * (h - b));
    AC = sqrt((a - e) * (a - e) + (b - f) * (b - f));
    BD = sqrt((c - g) * (c - g) + (d - h) * (d - h));
    abc = ((a - c) * (c - e) + (b - d) * (d - f)) / AB / BC;
    bcd = ((c - e) * (e - g) + (d - f) * (f - h)) / BC / CD;
    cda = ((e - g) * (g - a) + (f - h) * (h - b)) / CD / DA;
    dab = ((g - a) * (a - c) + (h - b) * (b - d)) / DA / AB;
    abc = acos(abc) + acos(bcd) + acos(cda) + acos(dab);
    if (((abc - (float)(2 * M_PI)) == 0) &&
        ((spase(AB, BC, AC) + spase(CD, DA, AC)) ==
         (spase(DA, AB, BD) + spase(CD, BC, BD)))) {
      printf("YES\n");
    } else {
      printf("NO\n");
    }
  }
  return 0;
}
