#include <bits/stdc++.h>
using namespace std;
const long long int MOD = 1000000007;
const long double PI = 2 * acos(0.0);
const vector<long long int> dx = {1, -1, 0, 0};
const vector<long long int> dy = {0, 0, 1, -1};
vector<long long int> ga(long long int n, bool oneIndexed = false) {
  vector<long long int> a;
  if (oneIndexed) a.push_back(0ll);
  for (long long int i = 0; i < n; i++) {
    long long int p;
    cin >> p;
    a.push_back(p);
  }
  return move(a);
}
vector<unsigned long long int> gau(unsigned long long int n,
                                   bool oneIndexed = false) {
  vector<unsigned long long int> a;
  if (oneIndexed) a.push_back(0llu);
  for (unsigned long long int i = 0; i < n; i++) {
    unsigned long long int p;
    cin >> p;
    a.push_back(p);
  }
  return move(a);
}
vector<string> gas(unsigned long long int n, bool oneIndexed = false) {
  vector<string> a;
  if (oneIndexed) a.push_back("");
  for (unsigned long long int i = 0; i < n; i++) {
    string p;
    cin >> p;
    a.push_back(p);
  }
  return move(a);
}
template <typename T, typename A>
void pa(vector<T, A> const &a, long long int begin = 0,
        long long int end = -1) {
  if (end == -1) end = (long long int)a.size() - 1;
  for (long long int i = begin; i <= end; i++) {
    cout << a[i] << " ";
  }
  cout << "\n";
}
template <typename T, typename A>
void papair(vector<T, A> const &a, long long int begin = 0,
            long long int end = -1) {
  if (end == -1) end = (long long int)a.size() - 1;
  for (long long int i = begin; i <= end; i++) {
    cout << a[i].first << " " << a[i].second << "\n";
  }
  cout << "\n";
}
void yes() { cout << "YES\n"; }
void no() { cout << "NO\n"; }
void yesno(int f) {
  if (f)
    yes();
  else
    no();
}
void solve() {
  vector<long long int> infreq, outfreq;
  long long int n, q;
  cin >> n >> q;
  vector<long long int> a = ga(n, 1);
  infreq = vector<long long int>(n + 1, 0);
  outfreq = vector<long long int>(n + 1, 0);
  while (q--) {
    long long int l, r;
    cin >> l >> r;
    infreq[l] += 1;
    outfreq[r] += 1;
  }
  vector<long long int> freq(n + 1, 0);
  for (long long int i = 1; i <= n; i++) {
    freq[i] += freq[i - 1];
    freq[i] += infreq[i];
    freq[i] -= outfreq[i - 1];
  }
  vector<pair<long long int, long long int> > data;
  for (long long int i = 1; i <= n; i++) data.push_back({freq[i], i});
  sort(data.begin(), data.end());
  sort(a.begin(), a.end());
  long long int s = 0;
  while (!data.empty()) {
    s += data.back().first * a.back();
    a.pop_back();
    data.pop_back();
  }
  cout << s;
}
int main(void) {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
