#include <iostream>
#include <string>
#include <cmath>

using namespace std;

double sinvalue( double v1x, double v1y, double v2x, double v2y )
{

	return ( v1x*v2y - v1y * v2x ) / sqrt( v1x * v1x + v1y * v1y ) * sqrt( v2x * v2x + v2y * v2y );
}


int main()
{
	double ax, ay, bx, by, cx, cy, dx, dy;
	double vecx_ab, vecy_ab, vecx_bc, vecy_bc, vecx_cd, vecy_cd, vecx_da, vecy_da;
	double sindab, sinabc, sinbcd, sincda;
	char tmp;
	while ( cin >> ax >> tmp >> ay >> tmp >> bx >> tmp >> by >> tmp >> cx >> tmp >> cy >> tmp >> dx >> tmp >> dy )
	{
		vecx_ab = bx - ax; vecy_ab = by - ay;
		vecx_bc = cx - bx; vecy_bc = cy - by;
		vecx_cd = dx - cy; vecy_cd = dy - cy;
		vecx_da = ax - dy; vecy_da = ay - dy;

		sindab = sinvalue( vecx_ab, vecy_ab, -vecx_da, -vecy_da );
		sinabc = sinvalue( vecx_bc, vecy_bc, -vecx_ab, -vecy_ab );
		sinbcd = sinvalue( vecx_cd, vecy_cd, -vecx_bc, -vecy_bc );
		sincda = sinvalue( vecx_da, vecy_da, -vecx_cd, -vecy_cd );

		if ( sindab > 0 && sinabc > 0 && sinbcd > 0 && sincda > 0 )
		{
			cout << "YES" << endl;
		}
		else 
		{
			cout << "NO" << endl;
		}
	}

	return 0;
}