#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvll;
const ll inf = 1e16;
const ll md = 1000000007;

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