from collections import *
from itertools import *
from functools import *
import math,sys
input = sys.stdin.readline

A = int(input())

ans = 2*(len(bin(A))-2)
L = 2*(len(bin(A))-2)
for i in range(2,L+1):
    
    cnt = 1
    while pow(i,cnt)<=A:
        cnt += 1
    ans = min(ans,i*(cnt))
print(ans)