用for語句循環不用函數？

int main()

{

int n,s=0;

cout<<"請輸入正整數n:";

cin>>n;

for(int i=1;i<=n;++i)

{

int m=1;

for(int j=1;j<=i;++j)

m*=j;

s+=m;

}

cout<<"\ns=1！+2！+3！+...+n！= "<<s;

}