// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
#include <cctype>
using namespace std;
#define ll long long
const int MOD=1e9+7;
int main() {
	ll n;cin>>n;
    // vector<int>h(n);
    ll sum=0;
    ll h,w;
    for(int i=0;i<n;i++){
        cin>>h>>w;
        sum+=w;
    }
    ll ans=0;
    for(int i=sum;i>=1;i--){
        for(int j=h;j>=1;j--){
            ans+=(i*j)%MOD;
            ans%=MOD;
        }
    }
    cout<<ans;
}
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