package quki.algorithm.string;

import java.util.HashMap;

import java.util.Scanner;

public class BOJ1672 {

public static void main(String[] args) {

HashMap<String, String> hm = new HashMap<>();

hm.put("AA", "A");

hm.put("AC", "A");

hm.put("CA", "A");

hm.put("GT", "A");

hm.put("TG", "A");

hm.put("GG", "G");

hm.put("AT", "G");

hm.put("CT", "G");

hm.put("TA", "G");

hm.put("TC", "G");

hm.put("AG", "C");

hm.put("GA", "C");

hm.put("CC", "C");

hm.put("GC", "T");

hm.put("CG", "T");

hm.put("TT", "T");

Scanner sc = new Scanner(System.in);

int N = sc.nextInt();

sc.nextLine();

String str = sc.nextLine();

char[] strArray = str.toCharArray();

for(int i = strArray.length-2; i>=0; i--){

char prev = strArray[i];

char curr = strArray[i+1];

StringBuilder key = new StringBuilder();

key.append(prev);

key.append(curr);

String replace = hm.get(key.toString());

char c = replace.charAt(0);

strArray[i+1] = 0;

strArray[i] = c;

}

StringBuilder ans = new StringBuilder();

for(int i = 0; i<strArray.length; i++){

char c = strArray[i];

if(c != 0){

ans.append(c);

}

}

System.out.println(ans.toString());

}

}