char* itoa(int x, char* str)
{
    int rem;
    int i=0, j=0;

    if (x < 0) {
        str[i++] = '-';
        x = -x;
        j++;
    }

    do {
        rem = x % 10;
        x /= 10;
        str[i++] = (char)(rem + '0');
    } while (x > 0);
    str[i--] = 0;

    while (j < i) {
        str[j] ^= str[i];
        str[i] ^= str[j];
        str[j] ^= str[i];
        j++; i--;
    }

    return str;
}