A = gets.to_i
loga = Math.log(A)
min = 10 ** 18
(2 .. A).each{|n|
    m = (loga / Math.log(n)).ceil
    if n*m < min
        warn [n, m, n*m].inspect
        min = n*m
    end
    break if n > min
    break if m == 2
}
puts min