// 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;
    for(int i=0;i<n;i++){
        ll x,y;cin>>x>>y;
        sum+=y;
    }
    ll ans=0;
    for(int i=sum;i>=1;i--){
        ans+=i%MOD;
        ans%=MOD;
    }
    cout<<ans;
}
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