def main():
    import sys
    input = sys.stdin.read().split()
    idx = 0
    H = int(input[idx])
    idx += 1
    W = int(input[idx])
    idx += 1
    S = []
    for _ in range(H):
        S.append(input[idx])
        idx += 1
    
    # 初始化四个方向的数组，尺寸为 (H+2) x (W+2)
    up = [[0]*(W+2) for _ in range(H+2)]
    down = [[0]*(W+2) for _ in range(H+2)]
    left = [[0]*(W+2) for _ in range(H+2)]
    right = [[0]*(W+2) for _ in range(H+2)]
    
    # 计算 up 数组
    for j in range(1, W+1):
        for i in range(1, H+1):
            if S[i-1][j-1] == '#':
                up[i][j] = up[i-1][j] + 1
            else:
                up[i][j] = 0
    
    # 计算 down 数组
    for j in range(1, W+1):
        for i in range(H, 0, -1):
            if S[i-1][j-1] == '#':
                down[i][j] = down[i+1][j] + 1
            else:
                down[i][j] = 0
    
    # 计算 left 数组
    for i in range(1, H+1):
        for j in range(1, W+1):
            if S[i-1][j-1] == '#':
                left[i][j] = left[i][j-1] + 1
            else:
                left[i][j] = 0
    
    # 计算 right 数组
    for i in range(1, H+1):
        for j in range(W, 0, -1):
            if S[i-1][j-1] == '#':
                right[i][j] = right[i][j+1] + 1
            else:
                right[i][j] = 0
    
    min_k = float('inf')
    for i in range(1, H+1):
        for j in range(1, W+1):
            if S[i-1][j-1] == '#':
                row_len = left[i][j] + right[i][j] - 1
                col_len = up[i][j] + down[i][j] - 1
                k = min(row_len, col_len)
                if k < min_k:
                    min_k = k
    print(min_k if min_k != float('inf') else 0)

if __name__ == '__main__':
    main()