#include <stdio.h>
#include <ctype.h>

#define STR_MAX 20
#define FALSE 0
#define TRUE 1

int chk_hex( str )
	char *str;
{
	while ( *str ) {
		if ( !isxdigit( *str ) )
			return FALSE;
		str++;
	}
	return TRUE;
}

main()
{
	char hex[STR_MAX];
	int num;

	printf("hexadecimal = ");
	scanf("%s", hex);
	if ( chk_hex( hex ) ) {
		sscanf(hex, "%x", &num);
		printf("%d\n", num);
		exit(0);
        } else {
		printf("not a hexiadecimal number\n");
		exit(1);
	}
}