#include<iostream>
#include<vector>
#include <stdlib.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    vector<int>A={1};
    for(int b=2;b<=n;b++){
        int t=0;    
        for(int i=0;i<(int)A.size();i++){
             t+= A[i]*b; 
                A[i] = t%10;
                t /= 10;                
        }
        while(t>0){
            A.push_back(t%10);
            t /= 10; 
        }
    }
    for(int i=A.size()-1;i>=0;i--)
        cout<<A[i];
    cout<<endl;
    system("pause");
}

## 2、