Problem H: 阶乘和

#include<stdio.h>
int main()
{
    int i=;
    int ret=;
    int sum=;
    int n;
    scanf("%d",&n);
    for(i=;i<=n;i++)
    {
        ret=ret*i;
        sum+=ret;
    }
    printf("%d\n",sum);
    return ;
}