#include<iostream>
#include<vector>

int main() 
{
	int desk_num;

	std::cin >> desk_num;

	long long students = 0;
	for (int i = 0; i < desk_num; i++)
	{
		long long chest_num, desk_num;
		std::cin >> chest_num >> desk_num;
		students += (((chest_num + 1) / 2) % 1000000007) * (desk_num % 1000000007);
		students %= 1000000007;
	}

	std::cout << students << std::endl;

	return 0;
}