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