Minimum Cost To Buy Oranges

You are given a bag of size 'W' kg and provided with the costs of packets with different weights of oranges as a list/array with the name 'cost'. Every i-th position in the cost denotes the price of 'i+1' kg packet of oranges.

If at any point in time the i-th cost is -1, it means that 'i+1' kg packet of orange is unavailable.

You are required to find the minimum total cost to buy exactly 'W' kg oranges and if it's not possible to buy precisely W kg oranges then print -1. There is an infinite supply of all available packet types.

Note :

Array index 'i' denotes the cost of (i+1)kg packet. 
Example: cost[0] is the cost of a 1kg packet of oranges.

Input Format :

The first line of each test case contains two single space-separated integers 'N' and 'W' where 'N' denotes the size of the array/list(cost), and 'W' is the bag's size.

The second line of each test case contains 'N' single space-separated integers denoting the values of the cost.

Output Format :

Print the minimum cost to buy exactly W kg oranges. If it's impossible, print "-1".

Note :

You are not required to print anything, it has already been taken care of. Just implement the function.

Constraints :

1 <= N <= 1000
1 <= W <= 1000
-1 <= cost[i] <= 1000000

Time Limit: 1sec