#include <cstdio>
using namespace std;

int main(){
    double xa, ya, xb, yb, xc, yc, xd, yd;
    while( scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",
                 &xa, &ya, &xb, &yb, &xc, &yc, &xd, &yc) != EOF ){
        bool f1 = (((xb-xd)*(ya-yb)-(yb-yd)*(xa-xb))*
                    ((xb-xd)*(yc-yb)-(yb-yd)*(xc-xb)) < 0);
        bool f2 = (((xa-xc)*(yb-ya)-(ya-yc)*(xb-xa))*
                    ((xa-xc)*(yd-ya)-(ya-yc)*(xd-xa)) < 0);
        if( f1 && f2 ){
            printf("YES\n");
        }else{
            printf("NO\n");
        }
    }
    return 0;
}