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