13.1. Система регистрации.

import java.util.*;

public class Main {

    public static void main(String[] args) {

        String s;
        int n,i;
        HashMap<String,Integer> nm = new HashMap<>();

        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        for(i=0 ; i< n; i++) {
            s = sc.next();
            if(!nm.containsKey(s)) {
                System.out.println("OK");
                nm.put(s,0);
            }
            else {
                nm.put(s, nm.get(s)+1);
                System.out.println(s + nm.get(s));
            }
        }
    }
}