dp(i, remain) that returns the minimum cost to paint remain walls starting from index i.remain <= 0, return 0 as the base case.i == n, return a large value (infinity) as the base case.ith wall: paint = cost[i] + dp(i + 1, remain - 1 - time[i]).ith wall: dontPaint = dp(i + 1, remain).paint and dontPaint.dp(0, n).