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

#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rep3(i,m,n) for(int (i)=m;(i)<=(n);(i)++)
#define rep3rev(i,m,n) for(int (i)=m;(i)>=(n);(i)--)
#define all(a) (a.begin()),(a.end())
#define rall(a) (a.rbegin()),(a.rend())
#define fi first
#define se second
#define pb push_back
#define eb emplace_back

using ll = long long;
using vll = vector<ll>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using P = pair<int, int>;

void Main(){
    int n; cin >> n;
    set<int> st;
    rep3(i, 0, 200005) st.insert(i);
    rep(i, n){
        int p; cin >> p;
        if(st.find(p) != st.end()) st.erase(p);
        cout << *st.begin() << endl;
    }
    return;
}

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    Main();
    return 0;
}
// Best practice
 
#include<bits/stdc++.h>
 
#define int         long long
#define pb          push_back
#define pf          emplace_front
#define all(a)      (a).begin(),(a).end()
#define rall(a)     (a).rbegin(),(a).rend()
#define pii         pair<int,int>
#define psi         pair<string,int>
#define vi          vector<int>
#define vpii        vector<pii>
#define vvi         vector<vi>
#define sz(x)       (int)(x).size()
#define x           first
#define y           second
#define endl        '\n'
#define tezz        ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define MOD         1000000007
#define hell        998244353
#define prec(n)     fixed<<setprecision(n)
#define ini(a, i)   memset(a, i, sizeof(a))
#define output(x)   cout << (x ? "YES" : "NO")<<endl;
using namespace std;

#define debug(vec) cout<<(#vec)<<" : [ "; for (auto& i: vec) cout<<i<<" "; cout<< "]" << endl
#define trace(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args);cout << endl; }
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
 cout << "[" << *it << ": " << a << "]\t";
 err(++it, args...);
} 

// const int dx[4] = { -1, 1, 0, 0};
// const int dy[4] = {0, 0, -1, 1};
// int dX[] = { -1, -1, -1, 0, 0, 1, 1, 1 };
// int dY[] = { -1, 0, 1, -1, 1, -1, 0, 1 };
 
 
// Code from Here -------------------------------------------------------------------------------

void solver(){
    int n, p;
    cin >> n;
    int c = 0;
    map<int,int> mp;
    for(int i=0; i<n; i++){
        cin >> p;
        mp[p]++;
        while(mp[c]){
            c++;
        }
        cout << c << endl;
    }    
}

signed main() {
    tezz
 
   

    int t=1;
    // cin >> t;
    while(t--){
        solver();
    }
 
    return 0;
}  