class SnakeGame:

    def __init__(self, width: int, height: int, food: List[List[int]]):
        self.snake = collections.deque([(0,0)])    # snake head is at the front
        self.snake_set = {(0,0) : 1}
        self.width = width
        self.height = height
        self.food = food
        self.food_index = 0
        self.movement = {'U': [-1, 0], 'L': [0, -1], 'R': [0, 1], 'D': [1, 0]}
        

    def move(self, direction: str) -> int:
        newHead = (self.snake[0][0] + self.movement[direction][0],
                   self.snake[0][1] + self.movement[direction][1])
        
        # Boundary conditions.
        crosses_boundary1 = newHead[0] < 0 or newHead[0] >= self.height
        crosses_boundary2 = newHead[1] < 0 or newHead[1] >= self.width
        
        # Checking if the snake bites itself.
        bites_itself = newHead in self.snake_set and newHead != self.snake[-1]
     
        # If any of the terminal conditions are satisfied, then we exit with rcode -1.
        if crosses_boundary1 or crosses_boundary2 or bites_itself:
            return -1

        # Note the food list could be empty at this point.
        next_food_item = self.food[self.food_index] if self.food_index < len(self.food) else None
        
        # If there's an available food item and it is on the cell occupied by the snake after the move, eat it
        if self.food_index < len(self.food) and \
            next_food_item[0] == newHead[0] and \
                next_food_item[1] == newHead[1]:  # eat food
            self.food_index += 1
        else:    # not eating food: delete tail                 
            tail = self.snake.pop()  
            del self.snake_set[tail]
            
        # A new head always gets added
        self.snake.appendleft(newHead)
        
        # Also add the head to the set
        self.snake_set[newHead] = 1

        return len(self.snake) - 1