Untitled

def explore(i, j):
    global solution, visited
    if (0 <= i < n) and (0 <= j < m) and (maze[i][j] != '#') and (not visited[i][j]):
        visited[i][j] = True
        if maze[i][j] == 'B':
            solution = True

        explore(i - 1, j)  # up
        explore(i + 1, j)  # down
        explore(i, j - 1)  # left
        explore(i, j + 1)  # right

def find(symbol):
    for i, row in enumerate(maze):
        j = row.find(symbol)
        if j >= 0:
            return (i, j)

n, m = [int(x) for x in input("Enter input: ").split()]
maze = [input() for _ in range(n)]
solution = False
visited = [[False] * m for _ in range(n)]

explore(*find('A'))

if solution:
    print("path from A to B exists")
else:
    print("no path")