import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;


public class encipher {
	
	public static void main(String[] args) throws Exception
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		
		while(true)
		{
			String s = in.readLine();
			if(s.equals("0"))
				break;
			int n = Integer.parseInt(s);
			s = in.readLine();
			String b = "";
			for (int i=0; i<s.length(); i++) {
				if (s.charAt(i) != ' ') {
					b += s.charAt(i);
				}
			}
			
			s = b;
			char[] r = new char[s.length()];
			
			int start = 0;
			int index = 0;
			for (int i=0; i<s.length(); i++) {
				if (index > s.length()) {
					index = ++start;
				}
				r[index] = s.charAt(i);
				index += n;
			}
			
			for (int i=0; i<r.length; i++) {
				System.out.print(Character.toUpperCase(r[i]));
			}
			System.out.println();
			
			
			
		}
	}

}