#include <bits/stdc++.h>
using namespace std;

int main()
{
int i;
int N;
long long C;
long long D;
long long iSum;
int iMod = 1000000007;

	cin >> N;

	iSum = 0;
	for( i = 0; i < N; i++ )
	{
		cin >> C;
		cin >> D;
		if( C % 2 == 0 )
			C /= 2;
		else
		{
			C /= 2;
			C++;
		}

		C %= iMod;
		D %= iMod;
		iSum += C * D;
		iSum %= iMod;
	}

	cout << iSum << endl;

	return 0;
}