#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
//#include "util.h"

using namespace std;
typedef long long lint;
typedef pair<lint, lint> Pii;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MOD ((lint)1000000007)

int main()
{
	lint N, c, d, ans = 0;
	cin >> N;
	for (lint i = 0; i < N; i++) {
		cin >> c >> d;
		ans += ((c + 1) / 2 % MOD) * (d % MOD);
		ans %= MOD;
	}
	cout << ans << endl;

	return 0;
}