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