#include<stdio.h>
int factorial (int n);
int main()
{
int n;
scanf("%d",&n);
while (n<=0)
		{
		scanf("%d",&n);
		if(n>0) break;
	}
printf("%d \n",factorial(n)); 
return 0;
}
int factorial(int n)
{
int i,fact=1;
for(i=1;i<=n;i++)
fact = fact*i;
return fact;
}