int main () {
int n,i,j,sum,S=0;
scanf("%d",&n);
sum=1;
for(i=n;i>=1;i--)
{for(j=i;j>=1;j--)
{
sum*=j;
}
S+=sum;}
printf("%d",S);
}
sum每次用完记得重置一下
#include<iostream>
using namespace std;
int main()
{
int n;
unsigned long long S = 0, sum = 1;
cin >> n;
int i, j;
for (i = 1; i <= n; i++)
{
for (j = 1; j <= i; j++)
{
sum *= j;
}
S += sum;
cout << sum << endl;
sum = 1;
}
cout << S;
return 0;
}