#include "bits/stdc++.h"
using namespace std;
using Graph = vector<vector<int>>;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i,n) for (ll i = 0; i < (n); ++i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const long long mod = 1e9 + 7;

ll gcd(ll a, ll b) {
	return b ? gcd(b, a % b) : a;
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}

int main() {
	ll n;
	cin >> n;
	
	ll ans=0;

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