def main():
  from sys import stdin
  readline=stdin.readline
  a = int(readline())
  ans = a 
  for i in range(2, a):
    now = 1
    for j in range(60):
      if i**j > a:
        tmp = i*j
        break
    if ans < tmp:
      break
    ans = tmp
  print(ans)
main()