## Goal

The rod cutting problem consists of cutting a rod in some pieces of different **length**, each having a specific **value**, such that the total value is maximized.

For example, consider that the rods of **length** 1, 2, 3 and 4 are marketable with respective **values** 1, 5, 8 and 9.

A rod of **length** 4 can then be cut in pieces in five different ways:

• 0×1 + 0×2 + 0×3 + 1×4 → total value: 0×1 + 0×5 + 0×8 + 1×9 = 9

• 1×1 + 0×2 + 1×3 + 0×4 → total value: 1×1 + 0×5 + 1×8 + 0×9 = 9

• 0×1 + 2×2 + 0×3 + 0×4 → total value: 0×1 + 2×5 + 0×8 + 0×9 = 10

• 2×1 + 1×2 + 0×3 + 0×4 → total value: 2×1 + 1×5 + 0×8 + 0×9 = 7

• 4×1 + 0×2 + 0×3 + 0×4 → total value: 4×1 + 0×5 + 0×8 + 0×9 = 4

The optimal cut is thus two pieces of length 2 which gives a total value of 10.

You can make pieces that are not marketable, but theses pieces will have a value of 0.

The rod cutting problem is the one-dimensional variant of the cutting stock problem. https://en.wikipedia.org/wiki/Cutting_stock_problem
Input

**First line:** `L` the length of the rod

**Second line:** `N` the number of different pieces that are marketable.

**Next **`N` lines: `length` `value` of each marketable piece, separated by a space.

Output

The maximum total value that can be obtained from the cut of the rod in different pieces.

Constraints

0 < `L` ≤ 100000

0 < `N` < 50

0 < `length` ≤ `L`

0 ≤ `value`

Example

Input

4
4
1 1
2 5
3 8
4 9