#include <bits/stdc++.h>
using namespace std;
int niz[1000005];
bool B[2000005];
int n,prefmex,br;
int main(){
 freopen("prefmex.in","r",stdin);
 freopen("prefmex.out","w",stdout);
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%d",&niz[i]);
int p=niz[i];
B[p]=1;
if(prefmex==p){
    prefmex++;
    while(B[prefmex]==1){
        prefmex++;
    }
}
printf("%d",prefmex);
printf("%c",' ');
cout<<endl;
}

}