int gcd(int a, int b)
{
    while (a != b && a != 1)
    {
        if (b == 1)
            a = 1;
        else if (a > b)
            a = a - b;
        else
            b = b - a;
    }
    
    return a;
}

int euler(int n)
{
    int i, t=0;

    if (n == 0)
        return 1;
    if (n < 0)
        n = -n;

    for (i = 1; i <= n; i++)
        if (gcd(n, i) == 1)
            t++;

    return t;
}