acm1181题： 除了写题,zqs还喜欢烤面包。

烤面包需要正反两面各烤一次，每个烤箱同时只能烤一个面包的一面，烤一面需要3分钟，现在他要烤N个面包，有M个烤箱，问烤完所有的面包需要多少时间

Input 有多组输入数据，第一行为一个数字case，代表有多少组输入数据 (case<=20)

以下每组数据一行有2个整数n，m，代表需要烤n个面包，有m个烤箱 （0<=N<=1000,1<=M<=1000)Output 一共case行，每行一个整数对应该组数据拷完所有面包需要多少时间Sample Input2

2 1

3 3

Sample Output12

6-acm1181 Question: In addition to written questions, zqs also like toast. Both sides need each toast grilled once, while each oven can bake a bread side, grilled side need three minutes, and now he wants to bake bread N, there are M oven, finished all the bread baked ask how long it takes Input plurality of sets of input data, the behavior of a first digital case, the number of the representative set of input data (case < = 20) the following data in each row have two integers n, m, n representative of a need to bake bread oven with m (0 < = N < = 1000,1 < = M < = 1000) Output total case lines of a pair of integers set of data should copy the time required to complete all the bread Sample Input2 2 1 3 3 Sample Output12 6