#include <bits/stdc++.h>
int main() {
  double a, A, b, B, c, C, d, D, v, V, w, W, x, X, y, Y;
  for (; ~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &a, &A, &b, &B, &c, &C, &d,
                &D);) {
    v = b - a;
    V = B - A;
    w = c - b;
    W = C - B;
    x = d - c;
    X = D - C;
    y = a - d;
    Y = A - D;
    puts(v * W - V * w > 0 && w * X - W * x > 0 && x * Y - X * y > 0 &&
                 y * V - Y * v > 0
             ? "YES"
             : "NO");
  }
}
