#include <iostream>

using namespace std;

int main() 
{
    int n;
    cin >> n;
    int sum = 1;
    if(n == 0)
    {
        cout << "1";
        return 0;
    }
    for(int i = n; i > 1;i--)
    {
        sum = sum * i;
    }
    
    cout << sum;
    
    return 0;
}