#include <bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define int long long
const int N = 1e6 + 5;
int32_t main()
{
IOS;
int n,T,v,l,r,ans=0;
cin >> n >> T;
vector <int> A;
vector <int> D;
for (int i=0;i<n;i++){
cin >> v;
A.push_back(v);
}
for (int i=0;i<n;i++){
D.push_back(0);
}
while (T--){
cin >> l >> r;
D[l-1]++;
D[r]--;
}
for (int i=1;i<n;i++){
D[i]=D[i-1]+D[i];
}
// for ( auto x :D){
// cout << x;
// }
sort(D.begin(),D.end());
sort(A.rbegin(),A.rend());
for (int i=0;i<n;i++){
ans=ans+(A[i]*D[i]);
//cout << A[i] << ' ' << D[i]<< endl;
//cout << ans << endl;
}
cout << ans;
}
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