Marisa got $n$ unused items, and she decided to put them in some boxes.
The $i^{th}$ item weighs $w_i$. Knowing each box can withstand a weight of $W$, what's the minimum number of boxes does she need to use?
### Input
- The first line contains 2 integers $n, W$.
- The second line contains $n$ integers $w_i$.
### Output
- Print the minimum number of boxes she need.
### Constraints
- $1 \le n \le 20$.
- $1 \le A_i \le W \le 10^9$.
### Example
Input:
```
4 5
1 2 3 4
```
Output:
```
2
```
