#include <bits/stdc++.h>
using namespace std;

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<(n);i++)
const ll mod = 1e9 + 7;
int main(void){
    ll n; cin >> n;
    ll ans = 0;
    rep(i, n){
        ll c, d; cin >> c >> d;

        if(c % 2 == 0){
            ans += (c / 2) % mod * d % mod;
        }else{
            ans += (c / 2 + 1) % mod * d % mod;
        }
        ans %= mod;

    }
    printf("%lld\n", ans);
    return 0;
}