import heapq

moves = {
    "<" : (0, -1),
    ">" : (0, 1),
    "v" : (1, 0),
    "^" : (-1, 0),
}

left_turn = {
    "<" : "v",
    ">" : "^",
    "v" : ">",
    "^" : "<",
}

right_turn = {
    "<" : "^",
    ">" : "v",
    "v" : "<",
    "^" : ">",
}

virages = {
    ("<","/") : "v",
    (">","/") : "^",
    ("^","/") : ">",
    ("v","/") : "<",
    (">","\\") : "v",
    ("<","\\") : "^",
    ("v","\\") : ">",
    ("^","\\") : "<",
}

def init():
    m = []
    carts = {}
    pos_carts = []
    with open('13', "r") as file:
        for i, line in enumerate(file.readlines()):
            m.append([])
            for j,c in enumerate(line):
                if c in ["<",">","v", "^"]:
                    m[-1].append("-")
                    carts[(i,j)] = (c,0)
                    pos_carts.append((i,j))
                else:
                    m[-1].append(c)

    heapq.heapify(pos_carts)
    return (pos_carts, carts, m)

def view(m):
    for l in m:
        for c in l:
            print(c, end='')
        print("")

def turn_intersection(cart):
    global left_turn, right_turn
    new_direction = cart[0]
    if cart[1] == 0:
        new_direction = left_turn[cart[0]]
    if cart[1] == 2:
        new_direction = right_turn[cart[0]]
    new_number = (cart[1]+1) % 3
    return (new_direction, new_number)

def turn_junction(cart, junction):
    global virages
    new_direction = virages[(cart[0],junction)]
    return (new_direction, cart[1])

def step(pos, m, carts, moves):
    new_pos = []
    removed = set()
    while len(pos)>0:
        p = heapq.heappop(pos)
        if(p in removed):
            continue
        cart = carts[p]
        move = moves[cart[0]]
        new_p = (p[0]+move[0], p[1]+move[1])
        try:
            assert(new_p[0]>=0)
            assert(new_p[1]>=0)
        except AssertionError:
            print("SHIT", p, new_p, move)
            return ([], [])
        new_cart = cart
        if m[new_p[0]][new_p[1]] == "+":
            new_cart = turn_intersection(cart)
        if m[new_p[0]][new_p[1]] in ["/","\\"]:
            new_cart = turn_junction(cart, m[new_p[0]][new_p[1]])

        del carts[p]
        if new_p in carts.keys():
            print("Crash at {}, {}".format(new_p[1], new_p[0]))
            del carts[new_p]
            if new_p in new_pos:
                new_pos.remove(new_p)
            removed.add(new_p)
            removed.add(p)
        else:
            new_pos.append(new_p)
            carts[new_p] = new_cart
    return (new_pos, carts)

(pos_carts, carts, m) = init()

while len(pos_carts)>1:
    pos_carts, carts = step(pos_carts, m, carts, moves)
print(pos_carts)