#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define rep(i,l,r) for (int i=(l); i<=(r); i++)
typedef long long ll;
using namespace std;

const int N=1010;
int n,a[N],res[N];

int main(){
	scanf("%d",&n);
	rep(i,1,n) scanf("%d",&a[i]);
	rep(i,1,n){
		int k=0;
		for (int j=n-i+1; j; j--) if (a[j]==j) { k=j; break; }
		if (!k){ puts("-1"); return 0; }
		res[i]=k;
		rep(j,k,n-i) a[j]=a[j+1];
	}
	for (int i=n; i; i--) printf("%d\n",res[i]);
	return 0;
}