#include <bits/stdc++.h>
using namespace std;

using ll=long long;
const int MOD=1e9+7;
ll ans;

signed main(){
  int n;cin>>n;
  while(n--){
    ll c,d;cin>>c>>d;
    c=(c+1)>>1;
    c%=MOD;d%=MOD;ans+=c*d;ans%=MOD;
  }
  cout<<ans<<endl;
}