A coordinate line has n segments, the i-th segment starts at the position li and ends at the position ri. We will denote such a segment as [li, ri].

You have suggested that one of the defined segments covers all others. In other words, there is such segment in the given set, which contains all other ones. Now you want to test your assumption. Find in the given set the segment which covers all other segments, and print its number. If such a segment doesn't exist, print -1.

Formally we will assume that segment [a, b] covers segment [c, d], if they meet this condition a ≤ c ≤ d ≤ b. 

Input

The first line contains integer n (1 ≤ n ≤ 105) — the number of segments. Next n lines contain the descriptions of the segments. The i-th line contains two space-separated integers li, ri (1 ≤ li ≤ ri ≤ 109) — the borders of the i-th segment.

It is guaranteed that no two segments coincide.

Output

Print a single integer — the number of the segment that covers all other segments in the set. If there's no solution, print -1.

The segments are numbered starting from 1 in the order in which they appear in the input.

Examples

Input

3
1 1
2 2
3 3


Output

-1


Input

6
1 5
2 3
1 10
7 10
7 7
10 10


Output

3
#include <bits/stdc++.h>
using namespace std;
template <typename T>
void read(T &x) {
  cin >> x;
}
template <typename T, typename T0>
void read(T &x, T0 &y) {
  cin >> x >> y;
}
template <typename T, typename T0, typename T1>
void read(T &x, T0 &y, T1 &z) {
  cin >> x >> y >> z;
}
template <typename T, typename T0, typename T1, typename T2>
void read(T &x, T0 &y, T1 &z, T2 &w) {
  cin >> x >> y >> z >> w;
}
template <typename T, typename T0>
void read(pair<T, T0> &p) {
  cin >> p.fst >> p.scd;
}
template <typename T>
void read(vector<T> &oneD, long long int n) {
  for (long long int(i) = 0; (i) < (n); ++(i)) {
    long long int x;
    read(x);
    oneD.push_back(x);
  }
}
template <typename T>
void read(T oneD[], long long int n) {
  for (long long int i = 0; i < n; i++) {
    read(oneD[i]);
  }
}
template <typename T>
void write(T &x) {
  cout << x << " ";
}
template <typename T, typename T0>
void write(T &x, T0 &y) {
  cout << x << " " << y << "\n";
}
template <typename T, typename T0, typename T1>
void write(T &x, T0 &y, T1 &z) {
  cout << x << " " << y << " " << z << "\n";
}
template <typename T, typename T0, typename T1, typename T2>
void write(T &x, T0 &y, T1 &z, T2 &w) {
  cout << x << " " << y << " " << z << " " << w << "\n";
}
template <typename T, typename T0>
void write(pair<T, T0> &p) {
  write(p.fst);
  write(p.scd);
  cout << endl;
}
template <typename T>
void write(vector<T> &oneD) {
  for (long long int i = 0; i < oneD.size(); i++) {
    write(oneD[i]);
  }
  cout << endl;
}
template <typename T>
void write(T oneD[], int n) {
  for (long long int i = 0; i < n; i++) {
    write(oneD[i]);
  }
  cout << endl;
}
template <typename T, typename T0>
void write(map<T, T0> &mpp) {
  for (auto it : mpp) {
    write(it.fst);
    cout << ": ";
    write(it.scd);
    cout << "\n";
  }
  cout << endl;
}
vector<long long int> seive;
void Seive() {
  const long long int maxn = 3000005;
  seive.resize(maxn);
  for (long long int(i) = 0; (i) < (maxn); ++(i)) seive[i] = i;
  seive[1] = -1;
  seive[0] = -1;
  for (long long int(i) = 2; (i) <= (maxn); (i) += (1))
    if (i == seive[i])
      for (long long int j = 2 * i; j < maxn; j += i)
        if (seive[j] == j) seive[j] = i;
}
long long int extended_GCD(long long int a, long long int b, long long int &x,
                           long long int &y) {
  if (a == 0) {
    x = 0;
    y = 1;
    return b;
  }
  long long int x1, y1;
  long long int gcd = extended_GCD(b % a, a, x1, y1);
  x = y1 - (b / a) * x1;
  y = x1;
  return gcd;
}
long long int modinv(long long int a, long long int mod = 1000000007) {
  long long int x, y;
  extended_GCD(a, mod, x, y);
  if (x < 0) x += mod;
  return x;
}
long long int find_x_CRT(long long int num[], long long int rem[],
                         long long int n) {
  long long int pro = 1;
  for (long long int(i) = 0; (i) < (n); ++(i)) pro *= num[i];
  long long int res = 0;
  for (long long int(i) = 0; (i) < (n); ++(i)) {
    long long int pp = pro / num[i];
    res += (rem[i] * modinv(pp, num[i]) * pp);
  }
  res %= pro;
  return res;
}
long long int power(long long int a, long long int b,
                    long long int m = 1000000007) {
  a %= m;
  long long int res = 1;
  while (b > 0) {
    if (b & 1) res = res * a % m;
    a = a * a % m;
    b >>= 1;
  }
  return res;
}
long long int powe(long long int a, long long int b,
                   long long int m = 1000000007) {
  long long int res = 1;
  while (b > 0) {
    if (b & 1) res = res * a;
    a = a * a;
    b >>= 1;
  }
  return res;
}
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
string getString(char x) {
  string s(1, x);
  return s;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long int n;
  read(n);
  long long int mi = 1e18, ma = 0;
  vector<pair<long long int, long long int>> a;
  for (long long int(i) = 0; (i) < (n); ++(i)) {
    long long int x, y;
    read(x, y);
    a.push_back({x, y});
    mi = min(mi, min(x, y));
    ma = max(ma, max(y, x));
  }
  long long int k = 1;
  for (auto x : a) {
    if (x.first == mi && x.second == ma) {
      cout << k;
      return 0;
    }
    k++;
  }
  cout << "-1";
  return 0;
}
