import java.util.*;
public class Functions {
public static void printFactorial(int n) {
//loop
if(n < 0) {
System.out.println("Invalid Number");
return;
}
int factorial = 1;
for(int i=n; i>=1; i--) {
factorial = factorial * i;
}
System.out.println(factorial);
return;
}
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
printFactorial(n);
}
}