/*
 * Program to compute binary from decimal (using recursion).
 *
 * Input:  Positive decimal integer N.
 *
 * Output:  Binary equivalent of N.
 */
#include <stdio.h>

/* Convert N to binary and print (does not print "\n" at the end) */
void dec_to_bin(int N) {
	int q;
	int r;
	if (N > 0) {
		r = N % 2;
		q = N / 2;
		dec_to_bin(q);
		printf("%d", r);
	}
}

/* Main program */
int main(void) {

	int N;
	int r;
	int q;

	printf("enter decimal integer (must not be <= 0)\n");
	if (scanf("%d", &N) != 1) {
		printf("Not a number\n");
	}
	else if (N < 0) {
		printf("The number must be positive\n");
	}
	else {
		dec_to_bin(N);
		printf("\n");
	}

	return 0;
}