import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;
import std.container;

alias sread = () => readln.chomp();
ulong bignum = 1_000_000_007;
alias Pair = Tuple!(long, "number", long, "times");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

void main()
{
    long n = lread();
    auto b = aryread();
    b.reverse();
    auto ans = new long[](0);

    while (n > 0)
    {
        long i;
        while (1)
        {
            if (i >= n)
            {
                writeln(-1);
                return;
            }

            if (b[i] == n - i)
            {
                ans ~= b[i];
                b = b[0 .. i] ~ b[i + 1 .. n];
                break;
            }

            i++;
        }
        n--;
    }
    foreach_reverse (e; ans)
    {
        e.writeln();
    }
}