#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	uint64_t N, c, d;
	cin >> N;
	uint64_t sum = 0;
	uint64_t mod = (uint64_t)(10e9 + 7);
	for (int i = 0; i < N; i++) {
		cin >> c >> d;
		sum += (c + 1) / 2 % mod * d % mod;
		sum %= mod;
	}
	cout << sum << endl;
	return 0;
}