#include <bits/stdc++.h>
using namespace std;
inline long long int __gcd(long long int a, long long int b);
void pdash(int n = 1);
int bitcount(long long int u);
long long int power(long long int x, long long int y);
long long int power(long long int x, long long int y, long long int z);
long long int modInverse(long long int n, long long int p);
long long int nCrF(long long int n, long long int r, long long int p);
void cordinate_compression(vector<int>& v);
void make_unique(vector<int>& vec);
void solve() {
  int n;
  cin >> n;
  vector<pair<int, int> > edge(n - 1);
  for (int i = 0; i < n - 1; i++) {
    cin >> edge[i].first >> edge[i].second;
    if (edge[i].first > edge[i].second) {
      swap(edge[i].first, edge[i].second);
    }
  }
  for (int i = 0; i < n - 1; i++) {
    if (edge[i].second != n) {
      cout << "NO\n";
      return;
    }
  }
  vector<int> cnt(n, 0);
  set<int> st;
  for (int i = 1; i < n; i++) {
    st.insert(i);
  }
  for (int i = 0; i < n - 1; i++) {
    cnt[edge[i].first]++;
    if (st.find(edge[i].first) != st.end()) {
      st.erase(edge[i].first);
    }
  }
  vector<pair<int, int> > ans;
  int curr = 1;
  for (int i = 1; i < n; i++)
    if (cnt[i]) {
      curr = n;
      cnt[i]--;
      while (cnt[i]) {
        if ((*st.begin()) > i) {
          cout << "NO\n";
          return;
        }
        ans.push_back({curr, *st.begin()});
        curr = *st.begin();
        st.erase(st.begin());
        cnt[i]--;
      }
      ans.push_back({curr, i});
    }
  cout << "YES\n";
  for (auto& j : ans) {
    cout << j.first << " " << j.second << "\n";
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
}
inline long long int __gcd(long long int a, long long int b) {
  if (a == 0 || b == 0) {
    return max(a, b);
  }
  long long int tempa, tempb;
  while (1) {
    if (a % b == 0)
      return b;
    else {
      tempa = a;
      tempb = b;
      a = tempb;
      b = tempa % tempb;
    }
  }
}
void pdash(int n) {
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < 30; j++) {
      cout << "-";
    }
    cout << "\n";
  }
}
long long int power(long long int x, long long int y) {
  long long int result = 1;
  while (y > 0) {
    if (y & 1) {
      result = (result * x);
    }
    y = y >> 1;
    x = (x * x);
  }
  return result;
}
long long int power(long long int x, long long int y, long long int z) {
  long long int result = 1;
  x = x % z;
  while (y > 0) {
    if (y & 1) {
      result = (result * x) % z;
    }
    y = y >> 1;
    x = (x * x) % z;
  }
  return result;
}
long long int modInverse(long long int n, long long int p) {
  return power(n, p - 2, p);
}
long long int nCrF(long long int n, long long int r, long long int p) {
  if (r == 0) return 1;
  long long int f[n + 1];
  f[0] = 1;
  for (long long int i = 1; i <= n; i++) f[i] = f[i - 1] * i % p;
  return (f[n] * modInverse(f[r], p) % p * modInverse(f[n - r], p) % p) % p;
}
void cordinate_compression(vector<int>& v) {
  vector<int> p = v;
  make_unique(p);
  for (int i = 0; i < (int)((v).size()); i++)
    v[i] = (int)(lower_bound(p.begin(), p.end(), v[i]) - p.begin());
}
void make_unique(vector<int>& vec) {
  sort(vec.begin(), vec.end());
  vec.erase(unique(vec.begin(), vec.end()), vec.end());
}
int bitcount(long long int u) {
  int cnt = 0;
  while (u) {
    u = u & (u - 1);
    cnt++;
  }
  return cnt;
}
