#include <bits/stdc++.h>
using namespace std;
class mstream {
 private:
  int res = 0;
  bool right = 0, sign = 0, space = 0, zero = 0;
  int width = 0, precision = 0, maxwidth = 1e6;
  string interval = "";
  const char* formstr(bool ri, bool si, bool sp, bool ze, bool wi, bool pr,
                      string ty) {
    string f = "%";
    if (ri && right) f += "-";
    if (si && sign) f += "+";
    if (sp && space) f += " ";
    if (ze && zero) f += "0";
    if (wi) f += "*";
    if (pr) f += ".*";
    f += ty;
    f += "%s";
    return f.c_str();
  }

 public:
  operator int() { return res; }
  mstream() {}
  mstream operator()() {
    res = 0;
    return *this;
  }
  mstream setright(bool n = 1) {
    right = n;
    return *this;
  }
  mstream setleft(bool n = 1) {
    right = !n;
    return *this;
  }
  mstream setsign(bool n = 1) {
    sign = n;
    return *this;
  }
  mstream notsign(bool n = 1) {
    sign = !n;
    return *this;
  }
  mstream setspace(bool n = 1) {
    space = n;
    return *this;
  }
  mstream notspace(bool n = 1) {
    space = !n;
    return *this;
  }
  mstream setzero(bool n = 1) {
    zero = n;
    return *this;
  }
  mstream notzero(bool n = 1) {
    zero = !n;
    return *this;
  }
  mstream setwidth(int n = 0) {
    width = n;
    return *this;
  }
  mstream setprecision(int n = 6) {
    precision = n;
    return *this;
  }
  mstream setmaxwidth(int n = 1e6) {
    maxwidth = n;
    return *this;
  }
  mstream setinterval(string n = " ") {
    interval = n;
    return *this;
  }
  mstream notinterval(string n = "") {
    interval = n;
    return *this;
  }
  mstream operator>>(int& x) {
    int r = scanf("%d", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(long long& x) {
    int r = scanf("%I64d", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(float& x) {
    int r = scanf("%f", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(double& x) {
    int r = scanf("%lf", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(char& x) {
    int r = scanf("%c", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(string& x) {
    char s[maxwidth + 1];
    int r = scanf("%s", s);
    if (r != EOF) x = s, res += r;
    return *this;
  }
  mstream operator<<(int x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 0, "d"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(long long x) {
    int r =
        printf(formstr(1, 1, 1, 1, 1, 0, "I64d"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(float x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 1, "f"), width, precision, x,
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(double x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 1, "lf"), width, precision, x,
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(char x) {
    int r = printf(formstr(1, 0, 0, 1, 1, 0, "c"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(string x) {
    int r = printf(formstr(1, 0, 0, 1, 1, 1, "s"), width, maxwidth, x.c_str(),
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
};
mstream mstr = mstream();
int main() {
  int n;
  mstr >> n;
  map<pair<int, int>, vector<int> > s;
  for (long long i = 0, i_TO = n; i < i_TO; i++) {
    int l, r;
    mstr >> l >> r;
    s[make_pair(l * 2 - 1, 1)].push_back(i + 1);
    s[make_pair(r * 2 + 1, 2)].push_back(i + 1);
  }
  set<int> t;
  int k = 0;
  for (pair<pair<int, int>, vector<int> > p : s)
    if (p.first.second == 1) {
      k += p.second.size();
      if (k > 1) t.insert(p.second.begin(), p.second.end());
    } else {
      for (int x : p.second)
        if (k > 1 && t.count(x)) mstr << x, exit(0);
      k -= p.second.size();
      if (k <= 1) t.clear();
    }
  mstr << -1;
}
