#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>



using namespace std;




int main() {

	long long int n;
	cin>>n;
	long long int ans=0;
	for(int i=0;i<n;i++){
		int a,b;
		cin>>a>>b;
		int t=a/2;
		if(a%2)t++;
		ans+=t*b;
		ans%=1000000007;
	}
	cout<<ans<<endl;
	return 0;
}