will.c

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

int par_ou_impar(char *S)
{
	int i, j, cont;

	j = strlen(S);

	for(i = 0; i < j; i++)
	{
		if(S[i] == '1')
			cont++;
	}

	return (cont % 2) ? 1 : 0;
}

int main(void)
{
	char *S;
	int num;

	scanf("%s", S);

	num = par_ou_impar(S);

	(num) ? puts(strcat(S, "0")) : puts(strcat(S, "1"));

	return 0;
}