#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
#define rep(i,n) for(int i=0;i<n;i++)

const ll mod = ll(1e9) + 7;
const int INF = 1<<29;

int main(){
    int n;
    cin >> n;
    ll ans = 0l;
    rep(i,n){
        ll c,d;
        cin >> c >> d;
        d %= mod;
        ll res = (c+1)/2;
        res %= mod;
        ans += res * d;
        ans %= mod;
    }
    cout << ans << endl;
    return 0;
}