C++如何用循环语句求1!+2!+3!+……+20！

#include<iostream>
using namespace std;
int main()
{
int j,k;
long int sum1=0,sum2;
for(k=1;k<=20;++k)
{
for(i=1,sum2=1;i<=k;++i)
sum2*=i;
sum1+=sum2;
}

cout<<"1!+2!+3!+……+20！="<<sum1<<endl;
return 0;
}