Greg's Workout

Greg 是一个健身者。现在有三种运动：$\text{chest}$，$\text{biceps}$，$\text{back}$。 Greg 会以 $$\text{chest} \to \text{biceps} \to \text{back} \to \text{chest} \to \text{biceps} \to \text{back} \to \ldots$$ 的规律（三个一组）做 $n$ 天运动，每天会做相应的运动 $a_i$ 次。问他做得最多的运动。 ### 输入 第一行一个整数 $n$。 接下来一行包含 $n$ 个整数，用空格隔开，分别为 $a_0, a_1, \ldots, a_{n-1}$，$a_i$ 表示第 $i$ 天做了 $a_i$ 次运动。 ### 输出 输出做得最多的运动。

Greg is a beginner bodybuilder. Today the gym coach gave him the training plan. All it had was $ n $ integers $ a_{1},a_{2},...,a_{n} $ . These numbers mean that Greg needs to do exactly $ n $ exercises today. Besides, Greg should repeat the $ i $ -th in order exercise $ a_{i} $ times. Greg now only does three types of exercises: "chest" exercises, "biceps" exercises and "back" exercises. Besides, his training is cyclic, that is, the first exercise he does is a "chest" one, the second one is "biceps", the third one is "back", the fourth one is "chest", the fifth one is "biceps", and so on to the $ n $ -th exercise. Now Greg wonders, which muscle will get the most exercise during his training. We know that the exercise Greg repeats the maximum number of times, trains the corresponding muscle the most. Help Greg, determine which muscle will get the most training.

The first line contains integer $ n $ $ (1<=n<=20) $ . The second line contains $ n $ integers $ a_{1},a_{2},...,a_{n} $ $ (1<=a_{i}<=25) $ — the number of times Greg repeats the exercises.

Print word "chest" (without the quotes), if the chest gets the most exercise, "biceps" (without the quotes), if the biceps gets the most exercise and print "back" (without the quotes) if the back gets the most exercise. It is guaranteed that the input is such that the answer to the problem is unambiguous.

2
2 8

biceps

3
5 1 10

back

7
3 3 2 7 9 6 8

chest

In the first sample Greg does 2 chest, 8 biceps and zero back exercises, so the biceps gets the most exercises. In the second sample Greg does 5 chest, 1 biceps and 10 back exercises, so the back gets the most exercises. In the third sample Greg does 18 chest, 12 biceps and 8 back exercises, so the chest gets the most exercise.