#include <bits/stdc++.h>
using namespace std;
string DBG_DLM(int& i) { return (i++ == 0 ? "" : ", "); }
template <class T>
ostream& operator<<(ostream& os, vector<T> v);
template <class T>
ostream& operator<<(ostream& os, set<T> v);
template <class T>
ostream& operator<<(ostream& os, queue<T> q);
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q);
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p);
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> mp);
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> mp);
template <int I, class TPL>
void DBG(ostream& os, TPL t) {}
template <int I, class TPL, class H, class... Ts>
void DBG(ostream& os, TPL t) {
  os << (I == 0 ? "" : ", ") << get<I>(t);
  DBG<I + 1, TPL, Ts...>(os, t);
}
template <class T, class K>
void DBG(ostream& os, pair<T, K> p, string delim) {
  os << "(" << p.first << delim << p.second << ")";
}
template <class... Ts>
ostream& operator<<(ostream& os, tuple<Ts...> t) {
  os << "(";
  DBG<0, tuple<Ts...>, Ts...>(os, t);
  os << ")";
  return os;
}
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p) {
  DBG(os, p, ", ");
  return os;
}
template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : v) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, set<T> s) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : s) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.front();
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.top();
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vpii = vector<pii>;
using vvpii = vector<vpii>;
using vvvpii = vector<vvpii>;
template <class A, class B>
bool amax(A& a, const B& b) {
  return b > a ? a = b, 1 : 0;
}
template <class A, class B>
bool amin(A& a, const B& b) {
  return b < a ? a = b, 1 : 0;
}
ll ri() {
  ll l;
  cin >> l;
  return l;
}
string rs() {
  string s;
  cin >> s;
  return s;
}
template <class T>
vector<int> compress(const vector<T>& orig) {
  vector<int> ret(orig.size());
  vector<T> a(orig);
  sort(a.begin(), a.end());
  a.erase(unique(a.begin(), a.end()), a.end());
  for (size_t i = 0; i < orig.size(); i++) {
    ret[i] = distance(a.begin(), lower_bound(a.begin(), a.end(), orig[i])) + 1;
  }
  return ret;
}
template <class V, class Merge>
struct SegmentTree {
  const int n;
  const V unit_value;
  vector<V> val;
  SegmentTree(int _n)
      : n(1 << (33 - __builtin_clz(_n - 1))),
        unit_value(Merge::unit()),
        val(n, unit_value) {}
  V get(int i) const { return val[i + n / 2]; }
  void set(int i, const V& v) { val[i + n / 2] = v; }
  void build() {
    for (int i = n / 2 - 1; i > 0; i--)
      val[i] = Merge::merge(val[i * 2 + 0], val[i * 2 + 1]);
  }
  void update(int i, const V& v) {
    i += n / 2;
    val[i] = v;
    while (i > 1) {
      i >>= 1;
      val[i] = Merge::merge(val[i * 2 + 0], val[i * 2 + 1]);
    }
  }
  V query(int l, int r) const {
    l = max(0, min(n / 2, l)) + n / 2;
    r = max(0, min(n / 2, r)) + n / 2;
    V ret = unit_value;
    for (; l < r; l >>= 1, r >>= 1) {
      if (l & 1) ret = Merge::merge(ret, val[l++]);
      if (r & 1) ret = Merge::merge(ret, val[--r]);
    }
    return ret;
  }
};
template <class V>
struct MergeRangeMinQ {
  static V merge(const V& l, const V& r) { return l < r ? l : r; }
  static V unit() { return numeric_limits<V>::max(); }
};
template <class V>
using SegTreeMin = SegmentTree<V, MergeRangeMinQ<V>>;
ll solve() {
  int n = ri();
  vi L(n), R(n), X(n * 2);
  for (int i = int(0); i < int(n); ++i) {
    L[i] = ri() - 1;
    R[i] = ri() - 1 + 1;
    X[i * 2] = L[i];
    X[i * 2 + 1] = R[i];
  }
  sort((X).begin(), (X).end());
  X.erase(unique(X.begin(), X.end()), X.end());
  for (auto&& i : L) i = lower_bound((X).begin(), (X).end(), i) - X.begin();
  for (auto&& i : R) i = lower_bound((X).begin(), (X).end(), i) - X.begin();
  int m = ((int)(X).size()) + 2;
  vi A(m);
  ;
  for (int i = int(0); i < int(n); ++i) {
    A[L[i]]++;
    A[R[i]]--;
  }
  for (int i = int(1); i < int(m); ++i) A[i] += A[i - 1];
  SegTreeMin<int> seg(m);
  for (int i = int(0); i < int(m); ++i) seg.set(i, A[i]);
  seg.build();
  for (int i = int(0); i < int(n); ++i) {
    if (seg.query(L[i], R[i]) >= 2) return i + 1;
  }
  return -1;
}
void Main() { cout << solve() << endl; }
signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  Main();
  return 0;
}
