利用c++递推与递归

#include <iostream>
using namespace std;

int pizza(int a)
{
    int sum = 2;
    for (int i = 1; i < a; ++i) {
        sum = sum + i + 1;
    }
    return sum;
}

int duck(int n)
{
    for (int i = 0; i < 7; ++i) {
        int v = (n + 1) * 2;
        n = v;
    }
    return n;
}

int main(void)
{
    int n;
    cin >> n;
    cout << pizza(n) << endl;
    
    cin >> n;
    cout << duck(n) << endl;
    return 0;
}