#include<iostream>
using namespace std;  
class digui {
public:
  long long fact(int x)
  {
  if (x == 1) {
    return (this->result = 1);
  }
  else {
    return (this->result=x*fact(x-1));
  }
  }
  void showresult()
  {
  cout << this->result << endl;
  }
  int a;
  long long result;
};
void func()
{
  digui dg;
  cin>>dg.a;
  dg.fact(dg.a);
  dg.showresult();
}
int main()
{
  func();
}