#include <bits/stdc++.h>
using namespace std;
int main() {
  char c;
  double xa, ya, xb, yb, xc, yc, xd, yd, ab, bc, cd, da, aa, bb, cc, dd;
  while (cin >> xa) {
    cin >> c >> ya >> c >> xb >> c >> yb >> c >> xc >> c >> yc >> c >> xd >>
        c >> yd;
    aa = sqrt((xb - xa) * (xb - xa));
    bb = sqrt((xc - xb) * (xc - xb));
    cc = sqrt((xd - xc) * (xd - xc));
    dd = sqrt((xa - xd) * (xa - xd));
    ab = ((xb - xa) * (xc - xb) + (yb - ya) * (yc - yb)) / (aa * bb);
    bc = ((xc - xb) * (xd - xc) + (yc - yb) * (yd - yc)) / (bb * cc);
    cd = ((xd - xc) * (xa - xd) + (yd - yc) * (ya - yd)) / (cc * dd);
    da = ((xa - xd) * (xb - xa) + (ya - yd) * (yb - ya)) / (dd * aa);
    if (ab * bc < 0 || bc * cd < 0 || cd * da < 0 || da * ab < 0)
      cout << "NO" << endl;
    else
      cout << "YES" << endl;
  }
  return 0;
}
