a, b = gets.chomp.split.map &:to_i
if a < 23
    if b < 23
        p 3
    elsif 25 < b
        p 0
    else
        if b == 23
            p 2
        elsif b == 24 
            p 1
        else
            p 0
        end
    end
elsif 25 < a
    p 3
else  # a = 23, 24, 25
    if b > 25 then b = 25 end
    p 3 - (b - a + 1)
end