#include <iostream>
#include <vector>
using namespace std;

int main() {
  int N;
  cin >> N;
  vector<int> p(N);
  for(int i=0; i<N; i++) cin >> p[i];

  vector<bool> ans(210000, true);
  int cur = 0;
  for (int i = 0; i < N; i++) {
    ans[p[i]] = false;
    for (int j=cur; j <= 210000; j++) {
      if (ans[j]) {
        cout << j << endl;
        cur = j;
        break;
      }else continue;
    }
  }
  return 0;
}
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef vector<vector<long long>> VVL;
typedef pair<int,int> P;
typedef tuple<int,int,int> tpl;

#define ALL(a)  (a).begin(),(a).end()
#define SORT(c) sort((c).begin(),(c).end())
#define REVERSE(c) reverse((c).begin(),(c).end())
#define EXIST(m,v) (m).find((v)) != (m).end()
#define LB(a,x) lower_bound((a).begin(), (a).end(), x) - (a).begin()
#define UB(a,x) upper_bound((a).begin(), (a).end(), x) - (a).begin()

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define RFOR(i,a,b) for(int i=(a)-1;i>=(b);--i)
#define RREP(i,n) RFOR(i,n,0)

#define en "\n"

constexpr double EPS = 1e-9;
constexpr double PI  = 3.1415926535897932;
constexpr int INF = 2147483647;
constexpr long long LINF = 1LL<<60;
constexpr long long MOD = 1000000007; // 998244353;

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

void Main(){
    int N; cin >> N;
    vector<bool> exist(200200,false);
    int pos = 0;
    REP(i,N){
        int p; cin >> p;
        exist[p] = true;
        while(exist[pos]) pos++;
        cout << pos << en;
    }
    return;
}

int main(void){
    cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(0);cout<<fixed<<setprecision(15);
    int t=1; //cin>>t;
    REP(_,t) Main();
    return 0;
}