#include<cstdio>
#include <iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>

using namespace std;
typedef long long ll;
typedef pair<int, int> Pr;

int N;
ll ans = 0;
ll mod = 1000000007;

int main()
{
	cin >> N;
	for (int i = 0; i < N; i++) {
		ll C, D;
		cin >> C >> D;
		C = (C + 1) / 2;
		ans = (ans + C%mod * (D%mod)) % mod;
	}
		cout << ans << endl;
	return 0;
}