#include <iostream>
#include <stdio.h>
using namespace std;

int main(){
	double xa,ya,xb,yb,xc,yc,xd,yd;
	double sab,sac,sbc,tab,tac,tbc;
	bool flag;
	
	while(scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",
	&xa,&ya,&xb,&yb,&xc,&yc,&xd,&yd)!=EOF)
	{
		sab=(yb-ya)/(xb-xa);
		sac=(yc-ya)/(xc-xa);
		sbc=(yc-yb)/(xc-xb);
		
		tab=ya-sab*xa;
		tac=ya-sac*xa;
		tbc=yb-sbc*xb;
		
		flag=(sab*xd+tab-yd>0&&sac*xd+tac-yd<0&&sbc*xd+tbc-yd<0);
		
		cout<<(flag?"YES\n":"NO\n");
	}
	return 0;
}