#include <iostream>
using namespace std;

int main() {
	int n, mod = 1000000007;
	unsigned long long int c, d, sum = 0;
	
	cin >> n;
	for(int i=0;i<n;++i){
		cin >> c >> d;
		
		sum = (sum +(((c + 1) / 2) % mod) * (d % mod)) % mod;
	}
	
	cout << sum << endl;
	
	return 0;
}