#define _USE_MATH_DEFINES	//M_PI
#include <iostream>			//std::cout, std::cin
#include <string>			//std::string
#include <vector>			//std::vector
#include <valarray>			//std::valarray	数値のみの一次配列
#include <algorithm>		//std::sort
#include <time.h>			//localtime_s
#include <cstdlib>			//abs
#include <cmath>			//abs, std::pow, sqrt, sin, cos,round,floor
#include <fstream>			//std::ifstream
#include <iomanip>			//std::setprecision
#include <random>			//std::random(C++11)
#include <numeric>			//std::accumulate

int main(void) {

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

	//MODULO 10^9+7用
	const unsigned int M = 1000000007;

	int N;
	std::cin >> N;

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

	std::cout << ans << std::endl;

}