#include <bits/stdc++.h>
#define PI 3.14159265359
using namespace std;
const int64_t mod = 1e9 + 7;

int main() {
	int64_t N;
	cin >> N;

	int64_t cnt = 0;
	for (int64_t i = 0; i < N; i++) {
		int64_t a, b;
		cin >> a >> b;

		cnt += (a + 1) / 2 % mod * (b % mod) % mod;
	}

	cout << cnt % mod << endl;
}