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<cstdio>
int main(){
    int n;
    long long ans=1;
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        ans*=i;
    }
    printf("%lld\n",ans);
}