func main()
	var s: []char :: cui@input()
	var ans: int :: 0
	for a(0, ^s - 1)
		for b(0, ^s - 1)
			var tmp: char
			do tmp :: s[a]
			do s[a] :: s[b]
			do s[b] :: tmp
			do ans :: [ans, s.toInt(&)].max()
			do tmp :: s[a]
			do s[a] :: s[b]
			do s[b] :: tmp
		end for
	end for
	do cui@print("\{ans}\n")
end func