A = int(input())
ans = 121
for i in range(2,61):
    lb = 0
    ub = 61
    while ub - lb > 1:
        mid = (ub + lb) // 2
        if A < pow(i,mid):
            ub = mid
        else:
            lb = mid
    if ub < 2:
        break
    ans = min(ans,i * ub)
print(ans)