#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define endl '\n'
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rep2(i,a,b) for(int i=int(a);i<int(b);i++)
#define pb emplace_back
#define all(x) (x).begin(),(x).end()
int mod=1e9+7;
int mod2=998244353;
const int INF=1e9;

signed main(){
	ll n;
	cin>>n;
	vector<ll> b(n);
	rep(i,n)cin>>b[i];

	vector<ll> ans;

	while(b.size()>0){
		ll tmp=0;
		ll id;
		rep(i,b.size()){
			if(b[i]==i+1&&tmp<b[i]){
				tmp=b[i];
				id=i;
			}
		}
		if(tmp==0){
			cout<<-1<<endl;
			return 0;
		}
		b.erase(b.begin()+id);
		ans.pb(tmp);
	}
	rep(i,n)cout<<ans[n-1-i]<<endl;
}

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