#include <bits/stdc++.h>
using namespace std;
template <class T>
T gcd(T a, T b) {
  return (b == 0) ? a : gcd(b, a % b);
}
const unsigned int MOD = 1000000007;
long long int inf = 1000000000000000000;
long long int MODI = 998244353;
template <class T>
T power(T a, long long int n) {
  T res = 1;
  while (n > 0) {
    if (n % 2) res = (res * a) % MOD;
    a = (a * a) % MOD, n = n / 2;
  }
  return res % MOD;
}
bool isprime(int n) {
  if (n <= 1) return false;
  for (int i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
bool issq(long long int n) {
  double d = n;
  double p1 = sqrt(d);
  long long int p2 = sqrt(n);
  return (p1 == p2);
}
long long int getSum(long long int n) {
  long long int sum = 0;
  while (n != 0) {
    sum = sum + n % 10;
    n = n / 10;
  }
  return sum;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, m;
  cin >> n >> m;
  vector<long long int> arr(n, 0);
  ;
  vector<long long int> val;
  ;
  for (long long int i = 0; i <= n - 1; i++) {
    long long int a;
    cin >> a;
    val.push_back(a);
  }
  long long int temp = m;
  while (temp--) {
    long long int l, r;
    cin >> l >> r;
    arr[l - 1]++;
    if (r < n) arr[r]--;
  }
  vector<pair<long long int, long long int> > pref;
  for (int i = 1; i < n; i++) arr[i] += arr[i - 1];
  ;
  sort(val.begin(), val.end(), greater<int>());
  ;
  ;
  sort(arr.begin(), arr.end(), greater<int>());
  ;
  long long int sum = 0;
  for (int i = 0; i < n; i++) sum += val[i] * arr[i];
  cout << sum;
}
