#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

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

const int MOD=1e9+7;

vector<ll> D(1000010);  
vector<vector<ll>> C(1000010);

void rec(ll u, ll p){
  D[u]=p;
  if(!C[u].empty()){
    for(auto x:C[u]) rec(x,p+1);
  }
}

int main() {
  int n;
  cin>>n;
  
  vector<ll> P(1000010);
  
  int a,b;
  rep(i,n){
    cin>>a>>b;
    P[b]=a;
    C[a].push_back(b);
  }
  
  ll root;
  for(ll i=1;i<=n;i++){
    if(P[i]==0){
      root=i;
      break;
    }
  }
  
  rec(root,0);
    
  ll ans=0;
  for(ll i=1;i<=n;i++){
    ans=(ans+(D[i]*(D[i]+1))%MOD/2)%MOD;
  }
  
  cout<<ans<<endl;

  return 0;
}