#include <bits/stdc++.h>
float inner_product(float ux, float uy, float vx, float vy) {
  return ux * vx + uy * vy;
}
float outer_product(float ux, float uy, float vx, float vy) {
  return ux * vy - vx * uy;
}
int main() {
  int i;
  int n;
  float input[8];
  int sign[4];
  int prev;
  int terminate = 0;
  int flag;
  float x1, x2, x3;
  float y1, y2, y3;
  while (1) {
    for (i = 0; i < 8; i++) {
      if (scanf("%f,", input + i) != 1) {
        terminate = 1;
      }
    }
    if (terminate) break;
    if (0) {
      for (i = 0; i < 8; i++) {
        printf("%f,", input[i]);
      }
      printf("\n");
    }
    x1 = input[4];
    y1 = input[5];
    x2 = input[6];
    y2 = input[7];
    for (i = 0; i < 4; i++) {
      x3 = input[i * 2];
      y3 = input[i * 2 + 1];
      sign[i] = (outer_product(x2 - x1, y2 - y1, x3 - x2, y3 - y2) > 0);
      x1 = x2;
      y1 = y2;
      x2 = x3;
      y2 = y3;
    }
    flag = 1;
    prev = sign[3];
    for (i = 0; i < 4; i++) {
      if (prev != sign[i]) {
        flag = 0;
      }
    }
    if (flag) {
      printf("Yes\n");
    } else {
      printf("No\n");
    }
  }
  return 0;
}
