Вычислить значение выражения n!+n^20

#include <iostream>
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/math/special_functions/factorials.hpp>
 
namespace mult = boost::multiprecision;
 
int main(int argc, char *argv[])
{
    int n;
    std::cin >> n;
    const int POWER = 20;
    
    mult::cpp_int number(n);
    mult::cpp_int p_n(mult::pow(number, POWER));
    mult::cpp_int fact(boost::math::factorial<double>(static_cast<double>(n)));
    
    std::cout << '\n' << p_n << " (Pow)\n+\n" << fact << " (Factorial)\n=\n" << p_n + fact << '\n';
}

#include <iostream>
using namespace std;
 
int main() {
    int n = 40;
    double fact   = n;
    double power  = n;
    for(size_t i = 1; i < n; i++)
    {
        fact *= i;
        if(i < 20)
        power*= n;
    }
    cout<<"n!   = "<<fact<<endl;
    cout<<"n^20 = "<<power<<endl;
    cout<<fact + power<<endl;
    return 0;
}

#include <iostream>
#include <cmath>
 
int main(){
    long long n = 40;
    
    double fact = pow(M_E, -n) * pow(n, n) * sqrt(2 * n * M_PI);
    double power = pow(n, 20);
    
    std::cout << "n!   = " << fact << std::endl;
    std::cout << "n^20 = " << power << std::endl;
    std::cout << "n! + n^20 = " << fact + power << std::endl;
}