#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod = 1e9+7;
int main(){
int n;cin>>n;
ll sum=0;
for(int i=0;i<n;i++){
ll x,y; cin>>x>>y;
x++;x/=2;
x%=mod;y%=mod;
sum += x * y;
sum %= mod;
}
cout << sum <<endl;
}