#include <cstdio>
#include <cstdlib>
#include <cstddef>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <iostream>
#include <iomanip>

#define ASDF (1000000007)

int main(void)
{
	long n;
	long c, d;
	long tot = 0;
	std::cin >> n;
	for (long i = 0; i < n; i++) {
		std::cin >> c >> d;
		tot = (tot + ((c + 1) / 2) * d) % ASDF;
	}
	std::cout << tot << std::endl;
	return 0;
}