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## 문제

Some people like finishing computer games in an extremely short time. Terry A. Smith is one of such and prefers role playing games particularly.

He is now trying to find a shorter play for one of the key events in a role playing game. In this event, a player is presented a kind of puzzle on a grid map with three rocks and three marked squares. The objective is to have all the rocks placed on the marked squares by controlling the hero of this game appropriately.

Figure 1: Example Map

The hero can move to the four adjacent squares, that is, to the north, east, south, and west, unless his move is blocked by walls or rocks. He can never enter squares occupied by walls. On the other hand, when he is moving to a square occupied by a rock, he pushes the rock in his moving direction. Nonetheless, he cannot push the rock if the next square is occupied by a wall or another rock and his move is blocked in this case. Also, he can only move one rock at a time. It is allowed to have rocks pass through marked squares.

Terry thinks he can reduce his playing time by finding the optimal way to move the rocks and then playing the event accordingly. However, it is too hard for him to find the solution of this puzzle by hand. So you are asked by him to write a program that finds the smallest number of steps for the maps given as the input. Here, each move from a square to its adjacent square is counted as one step.

## 입력

The input is a sequence of datasets. Each dataset has the following format:

W H
Row1
...
RowH


W and H are the width and height of the map (4 ≤ WH ≤ 16). Rowi denotes the i-th row of the map and consists of W characters. Each character represents a square and is one of the following: ‘#’ (wall), ‘.’ (floor), ‘*’ (rock), ‘_’ (marked square), and ‘@’ (hero). Each map contains exactly three rocks, three marked squares, and one hero. The outermost squares are always occupied by walls. You may assume that the number of non-wall squares does not exceed fifty. It is also guaranteed that there is at least one solution for every map.

The input is terminated by a line with two zeros. This line is not part of any datasets and should not be processed.

## 출력

For each dataset, print the smallest number of steps in a line.

## 예제 입력 1

7 6
#######
#.._..#
#.*.*.#
#.@.*.#
#_..._#
#######
10 13
##########
####___###
####...###
####...###
#####.####
#.....#..#
#.#*.*.*.#
#...###..#
###.#.#.##
###.#.#.##
###.....##
###..@..##
##########
0 0


## 예제 출력 1

15
118