#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

struct edge{
	int to;
	int cap;
	int rev;
	bool is_rev;
};

int Ford_Fulkerson_dfs(vector<vector<edge> > &G, int pos, int flow, vector<bool> &used, int t){
	if(pos == t){
		return flow;
	}else{
		used[pos] = true;
		for(int i=0; i<G[pos].size(); i++){
			if(!used[G[pos][i].to] && G[pos][i].cap >0){
				int myflow = Ford_Fulkerson_dfs(G, G[pos][i].to, min(flow, G[pos][i].cap), used, t);
				if(myflow > 0){
					G[pos][i].cap -= myflow;
					G[ G[pos][i].to ][ G[pos][i].rev ].cap += myflow;
					return myflow;
				}
			}
		}
		return 0;
	}
}

int Ford_Fulkerson(vector<vector<edge> > &G, int s, int t){
	const int INF = 100000000;
	int flow=0;
	for(;;){
		vector<bool> used(G.size(), false);
		int f = Ford_Fulkerson_dfs(G, s, INF, used, t);
		if(f==0) break;
		else flow += f;
	}
	return flow;
}

void add_edge(vector<vector<edge> > &G, int from, int to, int cap){
	G[from].push_back( (edge){to, cap, (int)G[to].size(), false} );
	G[to].push_back( (edge){from, 0, (int)G[from].size()-1, true} );
}


int main(){
	int N;
	cin >> N;
	vector<int> A(N);
	for(int i=0; i<N; i++){
		cin >> A[i];
	}

	vector<vector<edge>> G(2*N+2);
	int s = 2*N;
	int t = 2*N+1;

	for(int i=0; i<N; i++){
		add_edge(G, s, i, 1);
		add_edge(G, N+i, t, 1);
		for(int j=0; j<N; j++){
			if(j == A[i]) continue;
			add_edge(G, i, N+j, 1);
		}
	}

	int f = Ford_Fulkerson(G, s,t);
	if(f != N){
		cout << -1 << endl;
		return 0;
	}

	for(int i=0; i<N; i++){
		for(int j=0; j<G[i].size(); j++){
			if(G[i][j].cap == 0 && G[i][j].is_rev == false){
				cout << G[i][j].to-N << endl;
			}
		}
	}


	return 0;
}