#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main(){
  int N; cin>>N;
  ll MOD = 1000000007;
  ll ans = 0;
  FOR(i,0,N){
    ll C,D;
    cin>>C>>D;
    ans += (((C+1)/2)%MOD)*D;
    ans %= MOD;
  }
  cout << ans << endl;
  return 0;
}