Tron - dictionnaires récalcitrants :(

import random
import sys
import math

WIDTH = 30
HEIGHT = 20


dirs = {'UP': (0, -1), 'RIGHT': (1, 0), 'DOWN': (0, 1), 'LEFT': (-1, 0)}

def idebug(*args):
    # return
    print(*args, file=sys.stderr)


def debug(*args):
    # return
    print(*args, file=sys.stderr)

def get_moves(x, y):
    moves = []
    for move, (dx, dy) in dirs.items():
        if (x + dx, y + dy) not in lights and 0 <= x + dx < WIDTH and 0 <= y + dy < HEIGHT:
            moves.append(move)
    debug(f'moves: {moves}')
    return moves

cars = {}
lights = []
# game loop
while True:
    # n: total number of players (2 to 4).
    # p: your player number (0 to 3).
    n, p = [int(i) for i in input().split()]
    idebug(n, p)
    for i in range(n):
        # x0: starting X coordinate of lightcycle (or -1)
        # y0: starting Y coordinate of lightcycle (or -1)
        # x1: starting X coordinate of lightcycle (can be the same as X0 if you play before this player)
        # y1: starting Y coordinate of lightcycle (can be the same as Y0 if you play before this player)
        x0, y0, x1, y1 = [int(j) for j in input().split()]
        idebug(x0, y0, x1, y1)
        if cars.get(i):
            cars.get(i).append((x1, y1))
        else:
            cars[i] = [(x1, y1)]

    debug(f'cars: {cars}')

    lights = []
    for c in cars.values():
        lights += c
    lights = set(lights)
    debug(f'lights: {lights}')
    debug(f'cars: {cars}')
    my_car = cars[0]
    debug(f'my car: {my_car}')
    my_pos = my_car.pop()
    debug(f'my_pos: {my_pos}')
    move = random.choice(get_moves(*my_pos))

    # A single line with UP, DOWN, LEFT or RIGHT
    print(move)