a,b=gets.split(" ")
if a.size!=b.size
    puts [a,b][a.size>b.size ? 0 : 1]
else
    (a.size).times{|i|
        if a[i]=="4"&&b[i]=="7"
            puts a;exit
        elsif a[i]=="7"&&b[i]=="4"
            puts b;exit
        elsif a[i]!=b[i]
            puts [a,b][a[i].to_i>b[i].to_i ? 0 : 1]
            exit
        end
    }
end