Buggy python submission (verdict: Runtime Error):
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

def BFS(node):
    for item in node.link_node:
        if item.is_serched == False:
            item.distance = node.distance + 1
            item.is_serched = True
    for item in node.link_node:
        BFS(item)
n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_list[1].is_serched = True
node_list[1].distance = 0
BFS(node_list[1])

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))
    

Fixed submission:
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

class queue:
    def __init__(self):
        self.top = 0
        self.bottom = 0
        self.que = []
    
    def dequeue(self):
        self.top = self.top + 1
        return self.que[self.top - 1]
    
    def enqueue(self, item):
        self.que.append(item)
        self.bottom = self.bottom + 1
    
    def is_empty(self):
        if self.top == self.bottom:
            return True
        else:
            return False

n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_que = queue()

node_list[1].distance = 0
node_que.enqueue(node_list[1])
while node_que.is_empty() == False:
    top_item = node_que.que[node_que.top]
    top_item.is_serched = True
    for item in top_item.link_node:
        if item.is_serched == False:
            node_que.enqueue(item)
            if item.distance == -1:
                item.distance = top_item.distance + 1
            elif item.distance > top_item.distance + 1:
                item.distance = top_item.distance + 1
    node_que.dequeue()

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))

Buggy python submission (verdict: Runtime Error):
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

class queue:
    def __init__(self):
        self.top = 0
        self.bottom = 0
        self.que = [None] * 100
    
    def dequeue(self):
        self.top = self.top + 1
        return self.que[self.top - 1]
    
    def enqueue(self, item):
        self.que[self.bottom] = item
        self.bottom = self.bottom + 1
    
    def is_empty(self):
        if self.top == self.bottom:
            return True
        else:
            return False

n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_que = queue()

node_list[1].distance = 0
node_que.enqueue(node_list[1])
while node_que.is_empty() == False:
    top_item = node_que.que[node_que.top]
    top_item.is_serched = True
    for item in top_item.link_node:
        if item.is_serched == False:
            node_que.enqueue(item)
            if item.distance == -1:
                item.distance = top_item.distance + 1
            elif item.distance > top_item.distance + 1:
                item.distance = top_item.distance + 1
    node_que.dequeue()

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))
    

Fixed submission:
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

class queue:
    def __init__(self):
        self.top = 0
        self.bottom = 0
        self.que = []
    
    def dequeue(self):
        self.top = self.top + 1
        return self.que[self.top - 1]
    
    def enqueue(self, item):
        self.que.append(item)
        self.bottom = self.bottom + 1
    
    def is_empty(self):
        if self.top == self.bottom:
            return True
        else:
            return False

n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_que = queue()

node_list[1].distance = 0
node_que.enqueue(node_list[1])
while node_que.is_empty() == False:
    top_item = node_que.que[node_que.top]
    top_item.is_serched = True
    for item in top_item.link_node:
        if item.is_serched == False:
            node_que.enqueue(item)
            if item.distance == -1:
                item.distance = top_item.distance + 1
            elif item.distance > top_item.distance + 1:
                item.distance = top_item.distance + 1
    node_que.dequeue()

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))

Buggy python submission (verdict: Runtime Error):
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

class queue:
    def __init__(self):
        self.top = 0
        self.bottom = 0
        self.que = [None] * 1000
    
    def dequeue(self):
        self.top = self.top + 1
        return self.que[self.top - 1]
    
    def enqueue(self, item):
        self.que[self.bottom] = item
        self.bottom = self.bottom + 1
    
    def is_empty(self):
        if self.top == self.bottom:
            return True
        else:
            return False

n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_que = queue()

node_list[1].distance = 0
node_que.enqueue(node_list[1])
while node_que.is_empty() == False:
    top_item = node_que.que[node_que.top]
    top_item.is_serched = True
    for item in top_item.link_node:
        if item.is_serched == False:
            node_que.enqueue(item)
            if item.distance == -1:
                item.distance = top_item.distance + 1
            elif item.distance > top_item.distance + 1:
                item.distance = top_item.distance + 1
    node_que.dequeue()

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))
    

Fixed submission:
class node:
    def __init__(self, num):
        self.number     = num
        self.distance   = -1
        self.link_node  = []
        self.is_serched = False

class queue:
    def __init__(self):
        self.top = 0
        self.bottom = 0
        self.que = []
    
    def dequeue(self):
        self.top = self.top + 1
        return self.que[self.top - 1]
    
    def enqueue(self, item):
        self.que.append(item)
        self.bottom = self.bottom + 1
    
    def is_empty(self):
        if self.top == self.bottom:
            return True
        else:
            return False

n = input()
node_list = [None] * (n + 1)

for i in xrange(1, n + 1):
    node_list[i] = node(i)

for i in xrange(1, n + 1):
    line = raw_input().split()
    for node_num in line[2 : ]:
        node_list[i].link_node.append(node_list[int(node_num)])

node_que = queue()

node_list[1].distance = 0
node_que.enqueue(node_list[1])
while node_que.is_empty() == False:
    top_item = node_que.que[node_que.top]
    top_item.is_serched = True
    for item in top_item.link_node:
        if item.is_serched == False:
            node_que.enqueue(item)
            if item.distance == -1:
                item.distance = top_item.distance + 1
            elif item.distance > top_item.distance + 1:
                item.distance = top_item.distance + 1
    node_que.dequeue()

for item in node_list[1 : ]:
    print '%s %s' % (str(item.number), str(item.distance))