#pragma GCC optimize("Ofast")
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<vector>
#include<string.h>
#include<math.h>
#include<map>
#include<iomanip>
#include<queue>

const long long INF = 1e17+7;
const long long MOD = 1e9+7;
const double PI=acos(-1);

using namespace std;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	unsigned long long sum=0;
	for(int i=0;i<n;i++){
		unsigned long long c,d;
		cin >> c >> d;
		long long tmp=((c+1)/2)%MOD;
		d%=MOD;
		sum+=(d*tmp)%MOD;
	}
	sum%=MOD;
	cout << sum << endl;
	return 0;
}