C++ :

#include<bits/stdc++.h>
using namespace std;
int n,q,a[200003],d[200003];
long long ans;
int main(){
	scanf("%d%d",&n,&q);
	for(int i=1;i<=n;++i)scanf("%d",&a[i]);
	int l,r;
	while(q--){
		scanf("%d%d",&l,&r);
		d[l]++,d[r+1]--;
	}
	for(int i=2;i<=n;++i)d[i]+=d[i-1];
	sort(a+1,a+n+1);sort(d+1,d+n+1);
	for(int i=1;i<=n;++i)ans+=(long long)d[i]*a[i];
	printf("%lld",ans);
	return 0;
}