package main

import (
    "fmt"
    "strconv"
    "strings"
)

type bign []int8

func main() {
    var n int
    fmt.Printf("> ")
    fmt.Scanf("%d", &n)
    a, err := assign("1")
    if err != nil {
        panic(err)
    }
    for i := 2; i <= n; i++ {
        a = mult(a, i)
    }
    /*for i := 0; i < ; i++ {
        a = mult(a, 2)
    }*/
    //a = mult(a, 50)
    fmt.Println(out(a))
}

func add(a bign, b bign) bign {
    c, _ := assign("0")
    p := new(bign)
    if len(a) > len(b) {
        p = &a
        for i := 0; i < len(a)-len(b); {
            b = append(b, 0)
        }
    } else {
        p = &b
        for i := 0; i < len(b)-len(a); {
            a = append(a, 0)
        }
    }
    for i := range *p {
        if len(c) == i+1 {
            c[i] += a[i] + b[i]
        } else {
            c = append(c, a[i]+b[i])
        }
        if c[i] >= 10 {
            c = append(c, (c[i]-c[i]%10)/10)
            c[i] = c[i] % 10
        }
    }
    return c
}
func mult(a bign, b int) bign {
    var c bign
    for i := 0; i < b; i++ {
        c = add(c, a)
    }
    return c
}

// a := assign("1 009 589")
// fmt.Println(a)    Output: [9, 8, 5, 9, 0, 0, 1]
func assign(n string) (bign, error) {
    n = strings.Replace(n, " ", "", -1)
    num := []rune(n)
    c := make(bign, 0)
    for i := len(num) - 1; i >= 0; i-- {
        a, err := strconv.Atoi(string(num[i]))
        c = append(c, int8(a))
        if err != nil {
            var d bign
            return d, err
        }
    }
    return c, nil
}

func out(a bign) string {
    var s string
    for i := len(a) - 1; i >= 0; i-- {
        if (i+1)%3 == 0 && i != len(a)-1 {
            s += " "
        }
        s += fmt.Sprint(a[i])
    }
    return s
}