package main

import . "fmt"
import . "sort"

func main() {
	var a int64
	Scan(&a)
	min := int64(1e18)
	for m:=2; m < 63; m++ {
		n:= Search(1e9, func(v int) bool {
			var x = int64(1)
			for i:=0;i<m; i++ {
				if x > a/int64(v) {
					return true
				}
				x*=int64(v)
				if x > a {
					return true
				}
			}
			return x > a
		})
		if int64(n)*int64(m)<min {
			min=int64(n)*int64(m)
		}
	}
	Println(min)
}