CF26C.Parquet

Once Bob decided to lay a parquet floor in his living room. The living room is of size n × m metres. Bob had planks of three types: a planks 1 × 2 meters, b planks 2 × 1 meters, and c planks 2 × 2 meters. Help Bob find out, if it is possible to parquet the living room with such a set of planks, and if it is possible, find one of the possible ways to do so. Bob doesn't have to use all the planks.

有一天，Bob 决定为他的客厅铺设木地板。客厅的尺寸为 $n \times m$ 米。Bob 拥有三种木板：$a$ 块 $1 \times 2$ 米的木板、$b$ 块 $2 \times 1$ 米的木板，以及 $c$ 块 $2 \times 2$ 米的木板。请帮助 Bob 判断：是否能用这些木板铺满整个客厅？若可以，请给出一种可行的铺设方案。注意：Bob 不必使用全部木板。

The first input line contains 5 space-separated integer numbers n, m, a, b, c (1 ≤ n, m ≤ 100, 0 ≤ a, b, c ≤ 104), n and m — the living room dimensions, a, b and c — amount of planks 1 × 2, 2 × 1 и 2 × 2 respectively. It's not allowed to turn the planks.

第一行输入包含 5 个用空格分隔的整数 $n$、$m$、$a$、$b$、$c$（$1 ≤ n, m ≤ 100$，$0 ≤ a, b, c ≤ 10^4$），其中 $n$ 和 $m$ 表示客厅的尺寸，$a$、$b$ 和 $c$ 分别表示 $1 × 2$、$2 × 1$ 和 $2 × 2$ 地板木板的数量。不允许旋转木板。

If it is not possible to parquet the room with such a set of planks, output IMPOSSIBLE. Otherwise output one of the possible ways to parquet the room — output n lines with m lower-case Latin letters each. Two squares with common sides should contain the same letters, if they belong to one and the same plank, and different letters otherwise. Different planks can be marked with one and the same letter (see examples). If the answer is not unique, output any.

如果无法用给定的木板集合铺满房间，则输出 IMPOSSIBLE。否则，输出一种可能的铺法——输出 n 行，每行包含 m 个小写拉丁字母。若两个具有公共边的方格属于同一块木板，则它们应包含相同的字母；否则应包含不同的字母。不同的木板可以使用相同的字母标记（参见示例）。若答案不唯一，输出任意一种即可。