#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n, a, b;
  cin >> n >> a >> b;
  vector<int> v(n-1);
  for(auto& x: v) cin >> x;
  vector<int> valid;
  for(int i = a; i <= b; i++) {
    v.push_back(i);
    if(*min_element(v.begin(), v.end()) == a && *max_element(v.begin(), v.end()) == b) valid.push_back(i);
    v.pop_back();
  }
  if(valid.size() == 0) valid.push_back(-1);
  for(auto x: valid) cout << x << "\n";
}