public f2 RemainingPoint(SG e)
 {
     if (e.Equals(sgms[0]))
     {
         return(c);
     }
     if (e.Equals(sgms[1]))
     {
         return(a);
     }
     if (e.Equals(sgms[2]))
     {
         return(b);
     }
     throw new Exception();
 }