#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>

using namespace std;
const int MOD = 1e9 + 7;

int main() {
	int n;
	long long c, d;
	long long ans = 0;

	cin >> n;
	vector<int> a(n, 0);
	for (int i = 0; i < n; i++) {
		cin >> c >> d;
		ans = (((c + 1) / 2 % MOD) * (d % MOD) + ans) % MOD;
	}
	cout << ans << endl;
	return 0;
}