import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args)  {
        StringBuilder sb = new StringBuilder();
        try(BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
            int n = Integer.parseInt(br.readLine());
            String[] split = br.readLine().split("\\s+");
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < split.length; j++) {
                    sb.append(split[j].charAt(i));
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(sb.toString());
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz