/*	Reads an non-negative integer from stdin and prints it
	on stdout in hexadecimal base;	*/

#include <stdio.h>
#include <stdlib.h>

#define MAX_LEN 100
#define ERR_MSG_NEG "Err: the number is negative"

int main ( void ) {

	unsigned int num;
	char buffer[MAX_LEN];

	if(fgets(buffer, MAX_LEN, stdin) == NULL)
		return 1;

	/*	Converts the input str to int, if the number
		is negative, puts an error message on stderr;	*/
	if((num = atoi(buffer)) < 0 ) {
		fprintf(stderr, ERR_MSG_NEG"\n");
		return 1;
	}
	
	/*	prints the integer in hexadecimal base;	*/
	printf("%X\n", num);
	return 0;
}