#include<stdio.h>
int main()
{
int n;
long long factorial = 1;
if(scanf("%d", &n)! = 1)
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;
}