12.输入一个数，求1! + 3! - 5! + 7! - 9! ……(2*n+1)!

#include<iostream>
using namespace std;
int JiShuJieCheng(int);

int main()
{
    int n;
    int sum=0;
    cout<<"please input an number : "<<endl;
    cin>>n;
    for(int j=1;j<=n;j++,j++)
    {
        sum+=JiShuJieCheng(j);
    }
    cout<<sum<<endl;
    return 0;
}

int JiShuJieCheng(int p)
{
    int m=1;
    for(int i=1;i<=p;i++)
    {
        m*=i;
    }
    return m;
}