#include <stdio.h>

int main(void)
{
   char colour;
 
   /* ask user for colour */
   printf ("Enter the colour of the light (R, G or Y): ");
   scanf ("%c", &colour);
 
   /* test if colour is red */
   if (colour == 'r' || colour == 'R')
      	printf ("STOP! \n");
   else
      	if (colour == 'y' || colour == 'Y') /* yellow colour test */
        	  printf ("CAUTION! \n");
      	else
        	if (colour == 'g' || colour == 'G') /* green colour test */
             		printf ("GO! \n");
          	else
             		/* if not Y or G or R then invalid colour */
             		printf ("INVALID COLOUR! \n");
 
return(0);
}