package main

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

func main() {
	X := nextInt()
	ans := 0
	for i := 2; i * i <= X; i++ {
		ans = i
	}
	if ans > 0 {
		fmt.Println(ans)
	}else {
		fmt.Println(X)
	}


}

var s = bufio.NewScanner(os.Stdin)

func next() string {
	s.Split(bufio.ScanWords)
	s.Scan()
	return s.Text()
}
func nextLine() string {
	s.Split(bufio.ScanLines)
	s.Scan()
	return s.Text()
}

func nextInt() int {
	i, e := strconv.Atoi(next())
	if e != nil {
		panic(e)
	}
	return i
}
func nextLong() int64 {
	i, e := strconv.ParseInt(next(), 10, 64)
	if e != nil {
		panic(e)
	}
	return i
}


func min(a int, b int) int {
	if a < b {
		return a
	}
	return b
}
func max(a int, b int) int {
	if a < b {
		return b
	}
	return a
}