#include <stdio.h>

int main(void) {

  double xa,ya,xb,yb,xc,yc,xd,yd;

  double angle1,angle2;
  double temp;
  double x,y;

  //üªACÆ¼üBDA é¢Í¼üACÆüªBDªð··êÎÊp`
  while(scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",&xa,&ya,&xb,&yb,&xc,&yc,&xd,&yd)!=EOF) {

    if(xa==xc) {

      temp=(yd-yb)*(xa-xb)/(xd-xb)+yb;

      if((temp>ya && temp>yc) || (temp<ya && temp<yc)) printf("NO\n");

      else printf("YES\n");

    }

    else if(xb==xd) {

      temp=(yc-ya)*(xb-xa)/(xc-xa)+ya;

      if((temp>yb && temp>yd) || (temp<yb && temp<yd)) printf("NO\n");

      else printf("YES\n");

    }

    else {

      angle1=(yc-ya)/(xc-xa);
      angle2=(yd-yb)/(xd-xb);

      x=((angle1*xa-angle2*xb)-ya+yb)/(angle1-angle2);
      y=angle1*(x-xa)+ya;

      if((x>xa && x>xc) || (x<xa && x<xc) || (x>xb && x>xd) || (x<xb && x<xd)) printf("NO\n");

      else printf("YES\n");

    }

  }

  return 0;

}

       