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.

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 a_i (1≤a_i≤2·10⁵) − the array elements.

Each of the following q lines contains two space-separated integers l_i and r_i (1≤l_i≤r_i≤n) − the i-th query.

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 C++. It is preferred to use the cin, cout streams or the %I64d specifier.