import sys
readline=sys.stdin.readline
write=sys.stdout.write
from math import gcd as GCD
import math
import itertools

A=int(readline())
ans=1<<30
for n in range(2,100):
    for m in range(1,100):
        if pow(n,m)>=A:
            ans=min(ans,n*m)
            break
print(ans)