#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define p(s) cout<<(s)<<endl
typedef long long ll;
using namespace std;
const ll mod=1e9+7;

int main(){
	int N;
	cin>>N;
	ll ans=0;
	REP(i,0,N){
		ll a,b;
		cin>>a>>b;
		a=((a+1)/2)%mod;
		b%=mod;
		ans+=a*b;
		ans%=mod;
	}
	p(ans);
	return 0;
}