def tourner_a_gauche (sens):
    if sens == "NORD":
        sens0="OUEST"
    elif sens == "EST":
        sens0="NORD"
    elif sens == "SUD":
        sens0="EST"
    else: sens0="SUD"
    return sens0

def tourner_a_droite (sens):
    if sens == "NORD":
        sens0="EST"
    elif sens == "EST":
        sens0="SUD"
    elif sens == "SUD":
        sens0="OUEST"
    else: sens0="NORD"
    return sens0