#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

s = gets.chomp

mx = s.to_i

s.size.times do |i|
    (i + 1).upto(s.size - 1) do |j|
        t = s.dup
        t[i, 1] = s[j]
        t[j, 1] = s[i]
        mx = [mx, t.to_i].max
    end
end

puts mx