#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	int N;cin >> N;
	ll ans = 0;
	for (int i = 0; i < N; ++i)
	{
		ll c,d;
		cin >> c >> d;
		ans += ((c+1)/2%MOD) * (d%MOD);
		ans %= MOD;
	}
	cout << ans << endl;
	return 0;
}