#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <math.h>
using namespace std;
typedef long long int ll;

constexpr ll mod=1e9+7;

int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	int q; cin >> q;
	ll res=0;
	while(q--){
		ll a,b; cin >> a >> b;
		a=(a+1)/2;
		(res+=a%mod*b%mod)%=mod;
	}
	cout << res << endl;
}