题目链接

题意：



题解：









AC代码

/*
    Author:zzugzx
    Lang:C++
    Blog:blog.csdn.net/qq_43756519
*/
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define endl '\n'
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
//const int mod=1e9+7;
const int mod=998244353;
const double eps = 1e-10;
const double pi=acos(-1.0);
const int maxn=1e6+10;
const ll inf=0x3f3f3f3f;
const int dir[4][2]={{0,1},{1,0},{0,-1},{-1,0}};

struct node{
    ll t,d;
}p[maxn];
bool cmp(node a,node b){
    return a.t*b.d<b.t*a.d;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int n;cin>>n;
    for(int i=1;i<=n;i++)cin>>p[i].t>>p[i].d;
    sort(p+1,p+1+n,cmp);
    ll ans=0,sum=0;
    for(int i=1;i<=n;i++){
        ans+=sum*p[i].d;
        sum+=2*p[i].t;
    }
    cout<<ans<<endl;
    return 0;
}