// Template
#include "bits/stdc++.h"
#define rep_override(x, y, z, name, ...) name
#define rep2(i, n) for (int i = 0; i < (int)(n); ++i)
#define rep3(i, l, r) for (int i = (int)(l); i < (int)(r); ++i)
#define rep(...) rep_override(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define per(i, n) for (ll i = (ll)(n) - 1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003LL;
template <typename T>
inline bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T> 
inline bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}
struct IOSET {
    IOSET() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(10);
    }
} ioset;
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &element : vec) is >> element;
    return is;
}
template <typename T>
vector<T> operator--(vector<T> &vec) {
    for (T &element : vec) --element;
    return vec;
}

// Main
int main() {
    int n;
    cin >> n;
    vector<int> p(n);
    cin >> p;
    vector<int> cnt(200020, 0);
    int ans = 0;
    rep(i, n) {
        ++cnt[p[i]];
        while (cnt[ans]) ++ans;
        cout << ans << "\n";
    }
}
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
using namespace std;


template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

int main(){
    int N;
    vector<int> p;
    cin >> N;
    unordered_set<int> us;
    for(int i=0; i < N; ++i){
        int tmp;
        cin >> tmp;
        
        p.push_back(tmp);
    }

    

    int min=0;
    
    for(int i=0; i < N; ++i){
        us.insert(p[i]);
        //int num=i;
        while(1){
            if(us.find(min) == us.end()){
                cout << min <<endl;
                break;
            }
            else{
                ++min;
            }
        }
    }
    return 0;
}