Calculating factorial manually (naively by running a loop) using GMP C++ Class Interface

test.cpp

#include <iostream>
#include <gmpxx.h>
#include <chrono>
using namespace std;
int main()
{
	int n; cin>>n;
	auto start=chrono::high_resolution_clock::now();
	mpz_class a=1;
	for(int i=2; i<=n; i++)
		a=a*i;
	cout<<a<<"\n";
	auto end=chrono::high_resolution_clock::now();
	chrono::duration<double> diff=end-start;
	cout<<"Time taken="<<diff.count()<<"s\n";
}