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