The little girl loves the problems on array queries very much. One day she came across a rather well-known problem: you've got an array of n elements (the elements of the array are indexed starting from 1); also, there are q queries, each one is defined by a pair of integers l i , r i (1 ≤ l i ≤ r i ≤ n). You need to find for each query the sum of elements of the array with indexes from l i to r i , inclusive. The little girl found the problem rather boring. She decided to reorder the array elements before replying to the queries in a way that makes the sum of query replies maximum possible. Your task is to find the value of this maximum sum.

输入描述:

The first line contains two space-separated integers n (1 ≤ n ≤ 2·105) and q (1 ≤ q ≤ 2·105) — the number of elements in the array and the number of queries, correspondingly.The next line contains n space-separated integers ai (1 ≤ ai ≤ 2·105) — the array elements.Each of the following q lines contains two space-separated integers li and ri (1 ≤ li ≤ ri ≤ n) — the i-th query.

输出描述:

In a single line print a single integer — the maximum sum of query replies after the array elements are reordered.Please, do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specifier.