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 <iostream>
using namespace std;
int main(){
    long n,i=2,t;cin>>t;n=t;
    for(;i<t;i++)n*=i;
    cout<<n<<endl;
}