line = gets.chomp.map(&:to_i)
#line = [1000, 1, 1000]
N, X, T = line

shortest_time = 0

if N <= X
    shortest_time = T
elsif N > X
    burn_time = N / X
    # 1
    if N % X != 0 # 8
        shortest_time = (burn_time * T) + T
    else
        shortest_time = T * burn_time
    end
end 

p shortest_time


