用循环的方法该怎么编写

#include <iostream>
int Factorial(int k)
{
    int i,sum=1;
    if (k == 0)
        return 1;

    for (i = 1;i <= k;i++)
        sum *= i;
    return sum;
}
int main()
{
    int n,i,sum=0;
    std::cin >> n;
    for (i = 0;i <= n;i++)
    {
        sum += Factorial(n) / (Factorial(i) * Factorial(n - i));
    }
    std::cout << sum << std::endl;
    
    return 0;
}