#include<iostream>
using namespace std;
int main()
{
	long long n,s=0,a,b,M=1e9+7;cin>>n;
	for(int i=0;i<n;i++)cin>>a>>b,s=(s+((((a+1LL)>>1)%M)*(b%M))%M)%M;
	cout<<s<<endl;
}