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