#include "bits/stdc++.h" using namespace std; typedef long long ll; typedef pair pii; typedef pair pll; const int INF = 1e9; const ll LINF = 1e18; template ostream& operator << (ostream& out,const pair& o){ out << "(" << o.first << "," << o.second << ")"; return out; } template ostream& operator << (ostream& out,const vector V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; } template ostream& operator << (ostream& out,const vector > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; } template ostream& operator << (ostream& out,const map mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; } /* 問題文============================================================ ================================================================= 解説============================================================= ================================================================ */ void solve(){ ll N; cin >> N; vector A(N); for(auto& in:A) cin >> in; set s(A.begin(),A.end()); if(s.size()==1){ if(N==1 && *s.begin()!=0){ cout << 0 << endl; return; } cout << -1 << endl; return; } vector flag(N); for(int i = 0; i < N;i++){ for(int j = 0; j < N;j++){ if(A[i]==j) continue; if(flag[j]==1)continue; cout << j << endl; flag[j] = 1; break; } } } int main(void) { cin.tie(0); ios_base::sync_with_stdio(false); solve(); return 0; }