#include <bits/stdc++.h>
using namespace std;

using  ll =          long long int;
using ull = unsigned long long int;
const char en ='\n';
const int  mod=1000000007;

int main(){
	cin.tie();
	ios::sync_with_stdio(false);

	ll n,c,d;
	cin>>n;
	ll sum=0;
	for(int i=0;i<n;i++){
		cin>>c>>d;
		sum+=(((c+1)/2)%mod)*(d%mod);
		sum%=mod;
	}
	cout<<sum<<en;

	return 0;
}