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

int f[1000001],n,a,indx,i;

int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);

freopen("prefmex.in","r",stdin);
freopen("prefmex.out","w",stdout);

cin>>n;
for(i=0;i<n;i++){
    cin>>a;
    f[a]=1;
    while(f[indx]) indx++;
    cout<<indx<<" ";
}












return 0;
}