#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <stack>
#include <set>
#include <cmath>
#include <algorithm>
using namespace std;

struct Vector{
	double x;
	double y;
};

double gaiseki(Vector* a , Vector* b){
	return (a->x)*(b->y)+(a->y)*(b->x);
}

int main(){
	double xa,ya,xb,yb,xc,yc,xd,yd;
	char c;
	while(cin>>xa>>c>>ya>>c>>xb>>c>>yb>>c>>xc>>c>>yc>>c>>xd>>c>>yd){
		Vector ab , bc , ac , da , bd , dc;
		ab.x=xb-xa;
		ab.y=yb-ya;
		bc.x=xc-xb;
		bc.y=yc-yb;
		ac.x=xc-xa;
		ac.y=yc-ya;
		da.x=xa-xd;
		da.y=ya-yd;
		bd.x=xd-xb;
		bd.y=xd-xb;
		dc.x=xc-xd;
		dc.y=yc-yd;
		double abac , bdbc , dadc;
		abac=gaiseki(&ab , &ac);
		bdbc=gaiseki(&bd , &bc);
		dadc=gaiseki(&da , &dc);
		if((abac<0 && bdbc<0 && dadc<0)||(abac>=0 && bdbc>=0 && dadc>=0 )) cout << "NO" << endl;
		else cout << "YES" << endl;
	}
	return 0; 
}