def robtom3_1():
    from random import sample
    from matplotlib import pyplot as plt
    urne = {-1, 0, 1}
    x, y, sortie = 0, 0, 0
    posisTomX = [0] ; posisTomY = [0]
    while y <= 1 and y >= -1 and x <= 9:
        n = sample(urne, 1)
        y = y + n[0]
        x = x + 1
        posisTomX.append(x)
        posisTomY.append(y)
    if y == -2 or y == 2:
        message = "TOM est tombé\nà l'eau"
    else:
        message = "TOM a passé \nle pont"
        sortie = 1
    plt.figure()
    plt.plot((0, 10), (-2, 2), ls = 'none') ; plt.xticks(range(11)) ; plt.yticks(range(-2, 3))
    plt.fill((0, 10, 10, 0), (-1, -1, 1, 1), alpha = 0.3, color = 'green')