#include<cstdio>
main(){double a,A,b,B,c,C,d,D,e;for(;~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",&a,&A,&b,&B,&c,&C,&d,&D);a-=b,b-=c,c-=d,d-=e,e=A,A-=B,B-=C,C-=D,D-=e,puts(a*B-A*b>0&&b*C-B*c>0&&c*D-C*d>0&&d*A-D*a>0?"YES":"NO"))e=a;}