from sys import maxsize
from collections import deque


a = int(input())

n, m = 2, 1
while n**m < a:
    m += 1

q = deque()
q.append((n, m))

visited = set()
ans = maxsize
while len(q) > 0:
    n, m = q.popleft()
    if n**m >= a and (n, m) not in visited:
        visited.add((n, m))
        ans = min(ans, n * m)
        q.append((n + 1, m - 1))
        q.append((n, m - 1))

print(ans)