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main.cpp
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main.cpp
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// #pragma GCC optimize("O3,unroll-loops")
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
#define lli long long int
int main() {
int n, q;
cin >> n >> q;
vector<int> v(n);
for (int &e : v) {
cin >> e;
}
sort(v.begin(), v.end());
// Observation 1: The maximum accessed elem must be max
// Observation 2: building the array if coefficients costs extra
// Observation 3: We need coefficients in order
// Observation 4: Increment segments faster than O(n)
vector<int> uses(n + 1);
for (int i = 0; i < q; i++) {
int l, r;
cin >> l >> r;
uses[--l]++;
uses[r]--;
}
uses.pop_back();
int rsum = 0;
for (int &e : uses) {
rsum += e;
e = rsum;
}
sort(uses.begin(), uses.end());
lli s = 0;
for (int i = n - 1; i >= 0; i--) {
s += ((lli)uses[i]) * ((lli)v[i]);
}
cout << s;
}