1！+2!+......n！

#include<stdio.h>
int main()
{
    int a=1 ,i=1 ,sum=0,n;

    scanf("%d",&n);

    while(i<=n)
    {
           a=a*i;
        sum=sum+a;
        i++;
    }

    printf("1!+......n!是：%d\n",sum);
    return 0;
}