#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;

#define mod ((ll)(1e9)+7)

int main(){
	int n;
	cin >> n;
	ll ans=0;
	for(int i=0; i<n; i++){
		ll c, d;
		cin >> c >> d;
		ll t=(((c+1)/2)%mod)*(d%mod)%mod;
		ans+=t;
		ans%=mod;
	}
	cout << ans << endl;
	return 0;
}