There are N piles of stones arranged in a row. The i-th pile has stones[i] stones. A move consists of merging exactly K consecutive piles into one pile, and the cost of this move is equal to the total number of stones in these K piles. Find the minimum cost to merge all piles of stones into one pile. If it is impossible, return -1. Example 1: Input: stones = [3,2,4,1], K = 2 Output: 20 Explanation: We start with [3, 2, 4, 1]. We merge [3, 2] for a cost of 5, and we are left with [5, 4, 1]. We merge [4, 1] for a cost of 5, and we are left with [5, 5]. We merge [5, 5] for a cost of 10, and we are left with [10]. The total cost was 20, and this is the minimum possible. Example 2: Input: stones = [3,2,4,1], K = 3 Output: -1 Explanation: After any merge operation, there are 2 piles left, and we can't merge anymore. So the task is impossible. Example 3: Input: stones = [3,5,1,2,6], K = 3 Output: 25 Explanation: We start with [3, 5, 1, 2, 6]. We merge [5, 1, 2] for a cost of 8, and we are left with [3, 8, 6]. We merge [3, 8, 6] for a cost of 17, and we are left with [17]. The total cost was 25, and this is the minimum possible. Note: 1 <= stones.length <= 30 2 <= K <= 30 1 <= stones[i] <= 100