#include<bits/stdc++.h>

using namespace std;
using ll=long long;
#define rep2(i, a, n) for(int i = (a); i < (n); i++)
#define rep(i, n) rep2(i,0,n)
#define mod 1000000007

int main(){
  cin.tie(nullptr);ios_base::sync_with_stdio(false);
  int n;cin>>n;
  ll c,d,ans=0;
  rep(i,n){
    cin>>c>>d;
    c=(c+1)/2%mod;
    d%=mod;
    ans+=c*d;
    ans%=mod;
  }
  cout<<ans<<endl;
}