def expected(player1, player2):
    """
    Calculate expected score of player1 vs player2 given elo rankings.

    Args:
        player1 (BaseAgent): Agent for whom the score is being calculated.
        player2 (BaseAgent): Agent against whom player1 played.

    Returns:
        The expected score of the matchup.

    """
    return 1 / (1 + 10 ** ((player2.elo - player1.elo) / 400))