#define _USE_MATH_DEFINES	//M_PI(π),M_SQRT2(√2)
#include <iostream>			//std::cout, std::cin
#include <string>			//std::string,std::to_string(C++11)
#include <vector>			//std::vector
#include <valarray>			//std::valarray
#include <algorithm>		//std::sort
#include <time.h>			//localtime_s
#include <cstdlib>			//abs
#include <cmath>			//abs,std::pow,sqrt,sin,cos,round,floor,ceil
#include <fstream>			//std::ifstream,std::ofstream
#include <iomanip>			//std::setprecision,std::setw,std::setfill
#include <random>			//std::random(C++11)
#include <numeric>			//std::accumulate
#include <functional>		//std::greater
#include <list>				//std::list

int main(void) {

	//test用
	//std::ifstream in("123.txt");
	//std::cin.rdbuf(in.rdbuf());

	const unsigned long long M = 1000000007;

	unsigned long long N = 0, C = 0, D = 0, ans = 0;
	std::cin >> N;

	for (int i = 0; i < N; i++) {
		std::cin >> C >> D;
		if (C % 2 == 0) {
			ans += ((C / 2) % M * (D%M))%M;
		}
		else {
			ans += ((C / 2 + 1) % M*(D%M)) % M;
		}
	}

	std::cout << ans%M << std::endl;
}