One day Masha came home and noticed n mice in the corridor of her flat. Of course, she shouted loudly, so scared mice started to run to the holes in the corridor.

The corridor can be represeted as a numeric axis with n mice and m holes on it. ith mouse is at the coordinate x_i, and jth hole — at coordinate p_j. jth hole has enough room for c_j mice, so not more than c_j mice can enter this hole.

What is the minimum sum of distances that mice have to go through so that they all can hide in the holes? If ith mouse goes to the hole j, then its distance is |x_i - p_j|.

Print the minimum sum of distances.

Input

The first line contains two integer numbers n, m (1 ≤ n, m ≤ 5000) — the number of mice and the number of holes, respectively.

The second line contains n integers x₁, x₂, ..., x_n ( - 10⁹ ≤ x_i ≤ 10⁹), where x_i is the coordinate of ith mouse.

Next m lines contain pairs of integer numbers p_j, c_j ( - 10⁹ ≤ p_j ≤ 10⁹, 1 ≤ c_j ≤ 5000), where p_j is the coordinate of jth hole, and c_j is the maximum number of mice that can hide in the hole j.

Output

Print one integer number — the minimum sum of distances. If there is no solution, print -1 instead.

Mice and Holes

Examples