from collections import deque

bridge_length, weight_limit, truck_weights = 2, 10, [7, 4, 5, 6]

bridge = deque([0] * bridge_length)
current_weight = 0
time = 0

for truck in truck_weights:
    while True:
        current_weight -= bridge.popleft()
        time += 1
        if current_weight + truck <= weight_limit:
            bridge.append(truck)
            current_weight += truck
            break
        else:
            bridge.append(0)

time += bridge_length
print(time)