/*

按权值从小到大排序，

两个树状数组维护权值小于等于并且在i左边的点的个数和权值

*/

#include<iostream>

#include<cstring>

#include<cstdio>

#include<algorithm>

using namespace std;

#define maxn 20005

#define ll long long

struct node{

    int w,x;

    bool operator<(const node & a)const {

        return w<a.w;

    }

}a[maxn];

int n;

ll bitcnt[maxn],bittot[maxn],sum;

void add1(int x,int val){//bitcnt

    for(int i=x;i<=;i+=i&-i)

        bitcnt[i]+=val;

}

void add2(int x,int val){//bittot

    for(int i=x;i<=;i+=i&-i)

        bittot[i]+=val;

}

ll query1(int x){

    ll res=;

    for(int i=x;i;i-=i&-i)

        res+=bitcnt[i];

    return res;

}

ll query2(int x){

    ll res=;

    for(int i=x;i;i-=i&-i)

        res+=bittot[i];

    return res;

}    

int main(){

    while(scanf("%d",&n)==){

        memset(bitcnt,,sizeof bitcnt);

        memset(bittot,,sizeof bittot);

        sum=;

        for(int i=;i<n;i++) scanf("%d%d",&a[i].w,&a[i].x);

        sort(a,a+n);

        ll ans=;

        for(int i=;i<n;i++){

            ll left_node=query1(a[i].x);

            ll left_total=query2(a[i].x);

            ans+=a[i].w*(left_node*a[i].x-left_total);

            ans+=a[i].w*((sum-left_total-(i-left_node)*a[i].x));

            sum+=a[i].x;

            add1(a[i].x,);

            add2(a[i].x,a[i].x);

        }

        printf("%lld\n",ans);

    }

    return ;

}