input = gets.chomp.split(' ')
l = input[0].to_i
r = input[1].to_i
c = input[2].to_i
change_arr = []
for i in l..r do
    place = i*c
    num = 1
    change = 0
    while true
        change = num*1000-place
        if change >= 0 then
            break
        else
            num = num + 1
        end
    end
    change_arr.push(change.to_i)
end
sorted_arr = change_arr.sort do |a, b|
  b <=> a
end
puts sorted_arr.last