#N^M >= A
import math

A = int(input())


M1 = math.floor(math.log(A))

M2 = math.ceil(math.log(A))

N1 = math.ceil(A ** (1 / M1))

N2 = math.ceil(A ** (1 / M2))

print(min(M1 * N1, M2* N2))