input = gets.chomp.split(" ").map{|i|i.to_i}

n = input[0]
x = input[1]
t = input[2]

count_x = n / x
amari_x = n % x


if amari_x == 0
  total_time = count_x * t
else
  total_time = (count_x + 1) * t
end

puts total_time