package main

import (
	"bufio"
	"fmt"
	"math/big"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	var a int64
	fmt.Fscan(in, &a)

	res := big.NewInt(1)
	for i := int64(2); i <= a; i++ {
		res.Mul(res, big.NewInt(i))
	}

	fmt.Println(res)
}