#include <iostream>
using namespace std;
int main() {
	long long N;
	long long C, D;
	long long mod = 1000000007;
	long long ans = 0;
	cin >> N;
	for (long i = 0; i < N; i++) {
		cin >> C >> D;
		ans += ((((C + 1) / 2)%mod)*(D%mod)) % mod;
	}
	cout << ans%mod << endl;
	return 0;
}