#include<cstdio>
#include<algorithm>
#include<cmath>

using namespace std;

class PointF
{
public:
	double x,y;
PointF(){}
	PointF(int X,int Y)
	{
		x=X;y=Y;
	}
	double fun(PointF p)
	{
		return sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y));
	}
};

PointF point[4];

double ab,ac,ad,bc,bd,cd;

void set()//準備
{
	ab=point[0].fun(point[1]);
	ac=point[0].fun(point[2]);
	ad=point[0].fun(point[3]);
	bc=point[1].fun(point[2]);
	bd=point[1].fun(point[3]);
	cd=point[2].fun(point[3]);
}

double check(double a,double b,double c)
{
	double S=(a+b+c)/2;
	return sqrt(S-a+S-b+S-c);
}

int main()
{
	while(scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",&point[0].x,&point[0].y,&point[1].x,&point[1].y,&point[2].x,&point[2].y,&point[3].x,&point[3].y)!=EOF)
	{
		set();
		if(check(ab,bc,ac)+check(ac,ad,cd)==check(ab,bd,ad)+check(bc,cd,bd))
		{
			printf("YES\n");
		}
		else printf("NO\n");
	}
	return 0;
}