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