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#include<bits/stdc++.h>
using namespace std;

int n;
vector<int> a,b;

int main(){

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    cin>>n;
    for(int i=0;i<n;i++){
        int t;
        cin>>t;
        b.push_back(t);
    }
    for(int i=1;i<=n;i++){
        bool f=1;
        for(int j=b.size()-1;j>=0;j--){
            if(b[j]==j+1){
                a.push_back(b[j]);
                b.erase(b.begin()+j);
                f=0;
                break;
            }
        }
        if(f){
            cout<<-1<<endl;
            return 0;
        }
    }
    for(int i=a.size()-1;i>=0;i--){
        cout<<a[i]<<endl;
    }

    return 0;
}

Measured memory_bytes: 256