def winning_player(players, payoffs):
    """
    The index of a winning player from a pair of payoff values

    Parameters
    ----------
    players : tuple
        A pair of player indexes
    payoffs : tuple
        A pair of payoffs for the two players

    Returns
    -------
    integer
        The index of the winning player or None if a draw
    """
    if payoffs[0] == payoffs[1]:
        return None
    else:
        winning_payoff = max(payoffs)
        winning_payoff_index = payoffs.index(winning_payoff)
        winner = players[winning_payoff_index]
        return winner