#include <bits/stdc++.h>
int main() {
  double a[8];
  while (~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", a, a + 1, a + 2, a + 3,
                a + 4, a + 5, a + 6, a + 7)) {
    bool ok = true;
    if ((a[0] - a[2]) * (a[4] - a[2]) + (a[1] - a[3]) * (a[5] - a[3]) < 0)
      ok = false;
    if ((a[2] - a[4]) * (a[6] - a[4]) + (a[3] - a[5]) * (a[7] - a[5]) < 0)
      ok = false;
    if ((a[4] - a[6]) * (a[0] - a[6]) + (a[5] - a[7]) * (a[1] - a[7]) < 0)
      ok = false;
    if ((a[6] - a[0]) * (a[2] - a[0]) + (a[7] - a[1]) * (a[3] - a[1]) < 0)
      ok = false;
    printf(ok ? "YES\n" : "NO\n");
  }
}
