Average of the digits (modular arithmetic+function)

#include <stdio.h>

double Average(long long n)
{
    long long r, q = n, s = 0, tot = 0;
    while(q > 0) {
        r = q % 10;
        s += r;
        q /= 10;
        tot++;
    }
    return (double)s / (double)tot;
}

int main()
{
    long long x; // as x <= 10^19
    scanf("%lld", &x);

    double avg = Average(x);

    printf("%lf\n", avg);

    return 0;
}