line = STDIN.gets
produceTime = line.slice(0, 1).to_i
produceNum = line.slice(2, 1).to_i
finishTime = line.slice(4, 1).to_i + 0.5
biscuitNum = 0
nextTime = produceTime
N = 20
N.times do |i|
    # p "i:" + i.to_s
    if i == nextTime
        biscuitNum += produceNum
        # p "biscuitNum: " + biscuitNum.to_s
        nextTime += produceTime
        # p "nextTime: " + nextTime.to_s
    end
    if i >= finishTime
        puts biscuitNum
        return
    end
end