#include 
#include 
#include 
#include 
using namespace std;

int rec(int x) {
    if(x < 2) {
        return 1;
    }
    return x * rec(x - 1);
}
int main()
{
    
    cout << rec(5) << endl;
  
    return 0;
}
// rec(5) = 5 * rec(4) = 5 * 24 = 120
// rec(4) = 4 * rec(3) = 4 * 6 = 24
// rec(3) = 3 * rec(2) = 3 * 2 = 6
// rec(2) = 2 * rec(1) = 2 * 1 = 2
// rec(1) = 1