#from statistics import median

#import collections

#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]

from fractions import gcd

from itertools import combinations,permutations,accumulate, product # (string,3) 3回

#from collections import deque

from collections import deque,defaultdict,Counter

import decimal

import re

import math



#

#

#

# pythonで無理なときは、pypyでやると正解するかも！！

#

#

# my_round_int = lambda x:np.round((x*2 + 1)//2)

# 四捨五入g

#

# インデックス系

# int min_y = max(0, i - 2), max_y = min(h - 1, i + 2);

# int min_x = max(0, j - 2), max_x = min(w - 1, j + 2);

#

#

import sys

sys.setrecursionlimit(10000000)

mod = 10**9 + 7

#mod = 9982443453

#mod = 998244353

from sys import stdin

readline = stdin.readline

def readInts():

  return list(map(int,readline().split()))

def readTuples():

    return tuple(map(int,readline().split()))

def I():

  return int(readline())

x = I()

ans = -1

for b in range(1,x+2):

    for p in range(2, x+2):

        if b**p > x:

            break

        ans = max(ans, b**p)

print(ans)

#from statistics import median

#import collections

#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]

from fractions import gcd

from itertools import combinations,permutations,accumulate, product # (string,3) 3回

#from collections import deque

from collections import deque,defaultdict,Counter

import decimal

import re

import math

import bisect

#

#

#

# pythonで無理なときは、pypyでやると正解するかも！！

#

#

# my_round_int = lambda x:np.round((x*2 + 1)//2)

# 四捨五入g

#

# インデックス系

# int min_y = max(0, i - 2), max_y = min(h - 1, i + 2);

# int min_x = max(0, j - 2), max_x = min(w - 1, j + 2);

#

#

import sys

sys.setrecursionlimit(10000000)

mod = 10**9 + 7

#mod = 9982443453

#mod = 998244353

from sys import stdin

readline = stdin.readline

def readInts():

  return list(map(int,readline().split()))

def readTuples():

    return tuple(map(int,readline().split()))

def I():

  return int(readline())

x = I()

ans = 1

for b in range(2,1001):

    for p in range(2,24):

        if b**p <= x:

            ans = max(ans,b**p)

        else:

            break

print(ans)

# from statistics import median
# import collections
# aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from fractions import gcd
from itertools import combinations, permutations, accumulate, product  # (string,3) 3回

# from collections import deque
from collections import deque, defaultdict, Counter
import decimal
import re
import math

#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#
# my_round_int = lambda x:np.round((x*2 + 1)//2)
# 四捨五入g
#
# インデックス系
# int min_y = max(0, i - 2), max_y = min(h - 1, i + 2);
# int min_x = max(0, j - 2), max_x = min(w - 1, j + 2);
#
#
import sys

sys.setrecursionlimit(10000000)
mod = 10**9 + 7
# mod = 9982443453
# mod = 998244353
from sys import stdin

readline = stdin.readline


def readInts():
    return list(map(int, readline().split()))


def readTuples():
    return tuple(map(int, readline().split()))


def I():
    return int(readline())


x = I()
ans = -1
for b in range(1, x + 2):
    for p in range(2, x + 2):
        if b**p > x:
            break
        ans = max(ans, b**p)
print(ans)

# from statistics import median
# import collections
# aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from fractions import gcd
from itertools import combinations, permutations, accumulate, product  # (string,3) 3回

# from collections import deque
from collections import deque, defaultdict, Counter
import decimal
import re
import math
import bisect

#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#
# my_round_int = lambda x:np.round((x*2 + 1)//2)
# 四捨五入g
#
# インデックス系
# int min_y = max(0, i - 2), max_y = min(h - 1, i + 2);
# int min_x = max(0, j - 2), max_x = min(w - 1, j + 2);
#
#
import sys

sys.setrecursionlimit(10000000)
mod = 10**9 + 7
# mod = 9982443453
# mod = 998244353
from sys import stdin

readline = stdin.readline


def readInts():
    return list(map(int, readline().split()))


def readTuples():
    return tuple(map(int, readline().split()))


def I():
    return int(readline())


x = I()
ans = 1
for b in range(2, 1001):
    for p in range(2, 24):
        if b**p <= x:
            ans = max(ans, b**p)
        else:
            break
print(ans)

+import bisect -ans = -1 -for b in range(1, x + 2): -    for p in range(2, x + 2): -        if b**p > x: +ans = 1 +for b in range(2, 1001): +    for p in range(2, 24): +        if b**p <= x: +            ans = max(ans, b**p) +        else: -        ans = max(ans, b**p)