#include <stdio.h>
#include <string.h>

#define STR_MAX 20

main()
{
	char yes_no[STR_MAX];
	char *y = "yes";
	char *n = "no";

	printf("answer with yes or no : ");
	scanf("%s", yes_no);
	if (strcmp(yes_no, y) == 0)
		printf("you said YES.\n");
	else if (strcmp(yes_no, n) == 0)
		printf("you said NO.\n");
	else
		printf("answer yes or no\n");

	exit(0);
}