#include <bits/stdc++.h>
#define rep(i,n) for(ll (i)=0;(i)<(n);(i)++)
#define repi(i,a,b) for(ll (i)=(a);(i)<(b);(i)++)
#define SIZE_OF_ARRAY(array)    (sizeof(array)/sizeof(array[0]))
typedef long long ll;
using namespace std;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;
  ll c,d;
  ll ans = 0;
  ll MOD = 1000000007;
  rep(i,n){
    cin >> c >> d;
    ans+=((c+1)/2*d)%MOD;
  }
  cout << ans << endl;
  return 0;
  }