kamenetsky_formula.cpp

// Since the result can be large 
// long long is used as return type
long long countdigits(int n){
    if(n <= 1)
        return n;
    else{
        double x = ((n * log10(n / M_E)) + (log10(2 * M_PI * n) / 2.0)); 
        return floor(x) + 1;
    }
}