Get Decimal Length (O(log log N) complexity)

#include <iostream>
#include <cmath>

/****************************************************/

template <class T>
int decimal_length(T n) { //requires cmath header
    return 1 + (int)floor(log10(n));
}

/****************************************************/

int main() {
    std::cout << decimal_length(11111111111111) << std::endl; //too lazy to implement big integers
}