#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

int main(){
	
	int n;
	cin>>n;
	mint ans = 0;
	rep(_,n){
		long long c,d;
		cin>>c>>d;
		c = (c+1)/2;
		mint an = c;
		an *= d;
		ans += an;
		//cout<<ans.val()<<endl;
	}
	cout<<ans.val()<<endl;
	return 0;
}