package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
)

func main() {
    n := InputInt()/2
    fmt.Println(n*n)
}

var sc = bufio.NewScanner(os.Stdin)
func InputInt() int {
    sc.Scan()
    i, e := strconv.Atoi(sc.Text())
    if e != nil {panic(e)}
    return i
}