import random

class Checkerboard:
    def __init__(self):
        self.board = [[' ' for _ in range(8)] for _ in range(8)]
        self.initialize_board()

    def initialize_board(self):
        for i in range(3):
            for j in range(0, 8, 2):
                self.board[i][j] = 'b'
                self.board[i][j + 1] = 'w'
        for i in range(5, 8):
            for j in range(1, 7, 2):
                self.board[i][j] = 'w'
                self.board[i][j + 1] = 'b'

    def print_board(self):
        for row in self.board:
            print(' '.join(row))

    def valid_moves(self, piece):
        moves = []
        if piece == 'b':
            direction = -1
        else:
            direction = 1
        for i in range(8):
            for j in range(8):
                if self.board[i][j] == piece:
                    if i + direction < 8 and self.board[i + direction][j + 1] == ' ':
                        moves.append((i, j, i + direction, j + 1))
                    if i + direction < 8 and j - 1 >= 0 and self.board[i + direction][j - 1] == 'w':
                        moves.append((i, j, i + direction, j - 1))
                    if i + direction < 8 and j + 1 < 8 and self.board[i + direction][j + 1] == 'w':
                        moves.append((i, j, i + direction, j + 1))
                    if i + direction < 8 and j - 1 >= 0 and self.board[i + direction][j - 1] == 'b':
                        moves.append((i, j, i + direction, j - 1))
        return moves

    def make_move(self, start, end):
        x1, y1, x2, y2 = start
        self.board[x1][y1], self.board[x2][y2] = self.board[x2][y2], self.board[x1][y1]
        if abs(x1 - x2) == 2:
            mid = (x1 + x2) // 2
            self.board[mid][(y1 + y2) // 2] = ' '

    def check_winner(self):
        if len(self.valid_moves('b')) == 0:
            return 'w'
        elif len(self.valid_moves('w')) == 0:
            return 'b'
        else:
            return None

def play_game(player1, player2):
    board = Checkerboard()
    while True:
        board.print_board()
        print("Player 1's turn")
        move = player1.get_move(board)
        if move is not None:
            board.make_move(*move)
        winner = board.check_winner()
        if winner is not None:
            print(f"Player {winner} wins!")
            break
        board.print_board()
        print("Player 2's turn")
        move = player2.get_move(board)
        if move is not None:
            board.make_move(*move)
        winner = board.check_winner()
        if winner is not None:
            print(f"Player {winner} wins!")
            break

class HumanPlayer:
    def get_move(self, board):
        while True:
            start = input("Enter the starting position (row col): ")
            start = list(map(int, start.split()))
            end = input("Enter the ending position (row col): ")
            end = list(map(int, end.split()))
            if (start[0], start[1]) in board.valid_moves('b') or (start[0], start[1]) in board.valid_mov