打表义不容辞

#include<iostream> 
using namespace std; 
int n[13] = {0,1,2,6,24,120,720,5040,40320,362880,3628800,39916800,479001600};
int k, sum;
int main(){
    cin >> k;
	for(int i = 1; i <= k; i++){
        sum += n[i];
    }
    cout << sum;
    return 0;
}