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

const ll N=pow(10,9)+7;

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