local ffi = require("ffi")
local C = ffi.C
ffi.cdef[[
long long atoll(const char*);
]]

local function lltonumber(str)
  return C.atoll(str)
end

local a = io.read()
a = lltonumber(a)

-- find min n*m where a <= n^m
-- 2 <= a <= 10^18

local function llmin(x, y) return x < y and x or y end
-- m = 1
local ans = a
-- m = 2
local min, max = 0LL, 1000000007LL
while 1LL < max - min do
  local mid = (min + max) / 2LL
  if a <= mid * mid then
    max = mid
  else
    min = mid
  end
end
ans = llmin(ans, max * 2LL)
-- 3 <= m
for i = 2, 1000001 do
  local li = 1LL * i
  local ta = a - 1LL
  local m = 1
  while li <= ta do
    m = m + 1
    ta = ta / li
  end
  ans = llmin(ans, li * m)
end

ans = tostring(ans):gsub("LL", "")
print(ans)