#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
int main(){
	int n;
	ll c,d;
	cin>>n;
	int ans=0;
	while(cin>>c>>d){
		c=(c+1)/2%mod;
		d%=mod;
		(ans+=c*d%mod)%=mod;
	}
	cout<<ans<<endl;
}