#include<iostream>
using namespace std;
int main(void){
	int n; cin >> n;
	long long ans = 0;
	long m = (int)1e9 + 7;
	for (int i = 0; i < n; i++){
		long long c, d;
		cin >> c >> d;
		c = (c + 1) / 2 % m;
		d %= m;
		ans += c * d;
		ans %= m;
	}
	cout << ans << endl;
	return 0;
}