Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
#include<stdio.h>
int main(void){
long long int a,ans,i;
ans=1;
scanf("%lld",&a);
for(i=1;i<=a;i++){
    ans=ans*i;
}
printf("%lld\n",ans);
return 0;
}