The cows have purchased a yogurt factory that makes world-famous Yucky Yogurt. Over the next N (1 Yucky Yogurt owns a warehouse that can store unused yogurt at a constant fee of S (1 Yucky wants to find a way to make weekly deliveries of输入描述 * Line 1: Two space-separated integers, N and S. * Lines 2..N+1: Line i+1 contains two space-separated integers: C_i and Y_i.输出描述 * Line 1: Line 1 contains a single integer: the minimum total cost to satisfy the yogurt schedule. Note that the total might be too large for a 32-bit integer.输入例子 4 5 88 200 89 400 97 300 91 500 输出例子 126900 Hint OUTPUT DETAILS: In week 1, produce 200 units of yogurt and deliver all of it. In week 2, produce 700 units: deliver 400 units while storing 300 units. In week 3, deliver the 300 units that were stored. In week 4, produce and deliver 500 units.