思路可能有问题 求指正 悬两关

#include <bits/stdc++.h>
using namespace std;
#define int unsigned long long
const int maxn = 3e5+100;
int a[maxn],l[maxn],r[maxn],w[maxn],s[maxn];
signed main(){
	int n,m;
	cin>>n>>m;
	for(int i = 1;i<=n;i++){
		cin>>a[i];
	}
	sort(a+1,a+1+n);
	for(int i = 1;i<=n;i++){
		l[i] = r[i] = i;
		if(i!=n)r[i] = upper_bound(a+1,a+1+n,a[i+1])-a-1;
		if(i!=1)l[i] = lower_bound(a+1,a+1+n,a[i-1])-a;
		w[i] = r[i]-l[i];
		s[i] = s[i-1]+w[i];
	}
	int x,y,ans = 0;
	for(int i = 1;i<=m;i++){
		cin>>x>>y;
		ans+=i*(s[n]/2-(s[n]-s[y]+s[x-1]));
	}
	cout<<ans*2;
	return 0;
}