a,b = gets.split
ta,tb = [a,b].map(&:to_i).map{|v| ("%012d" % v).chars.map(&:to_i) }
j = 12.times.find {|i| ta[i] != tb[i] }

if ta[j] == 4 && tb[j] == 7
    puts a
elsif ta[j] == 7 && tb[j] == 4
    puts b
else
    puts ta[j] > tb[j] ? a : b 
end