Walking to a friend in the plaza

The map of a plaza in a metaverse social network is given as the grid plaza. '.' is a cell an avatar can walk on, '#' is a wall, 'A' is the cell where my avatar stands, and 'B' is the cell where my friend's avatar stands. In one step, an avatar moves to an adjacent cell above, below, to the left, or to the right. It cannot move into a wall or off the map.

Complete the function solution, which returns the smallest number of steps my avatar needs to reach my friend's cell. If my avatar cannot reach my friend, return -1.

Function

solution(plaza)

Constraints

• The length of plaza is from 1 to 20.
• The strings in plaza all have the same length, which is from 1 to 20.
• The strings in plaza consist only of '.', '#', 'A', and 'B', and 'A' and 'B' each appear exactly once in the whole map.

Examples

Starter code

def solution(plaza):
    answer = 0
    return answer