You are given an integer array cost where cost[i] is the cost of the i-th step on a staircase. Once you pay the cost, you can climb either one or two steps.
You can start from either step index 0 or step index 1. Return the minimum cost to reach the top of the staircase (one step past the last element).
Input: cost = [10, 15, 20] Output: 15 Explanation: Start at index 1, pay 15, jump two steps to the top.
Input: cost = [1, 100, 1, 1, 1, 100, 1, 1, 100, 1] Output: 6 Explanation: Take the cheap steps: 0->2->4->5->7->8->10, paying 1+1+1+1+1+1 = 6.
cost = [10, 15, 20]