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

const ll MOD = 1e9 + 7;

int main(){
	int N;
	cin >> N;

	ll res = 0;
	while(N--){
		int C, D;
		cin >> C >> D;

		C = (C + 1) / 2;

		C %= MOD;
		D %= MOD;

		res = (res + C * D % MOD) % MOD;
	}

	cout << res << endl;
	return 0;
}