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

void itoar(char *s, int x);

/* converts first arg to int, puts it to output with itoar */
int main(int argc, char *argv[])
{
    if (argc < 2)
        return 1;
    int x = atoi(argv[1]);
    char s[strlen(argv[1])+1];
    itoar(s, x);
    printf("%s\n", s);
    return 0;
}

char * utoar(char *s, unsigned x);

/* itoa: writes int x to string s in decimal
 * recursive implementation */
void itoar(char *s, int x)
{
    unsigned y = (x < 0) ? *(s++) = '-', -x : x;
    s = utoar(s, y);
    *s = '\0';
}

/* utoar: helper for itoa */
char * utoar(char *s, unsigned x)
{
    if (x / 10)
        s = utoar(s, x / 10);
    *s = x % 10 + '0';
    return s+1;
}