import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
 
public class Main {
	public static void main(String[] args) throws NumberFormatException,
	IOException {Solve solve = new Solve();solve.solve();}
}
class Solve{
	void dump(int[]a){for(int i=0;i<a.length;i++)
		System.out.print(a[i]+" ");System.out.println();};
    void solve() throws NumberFormatException, IOException{
        final ContestScanner in = new ContestScanner();
        Writer out = new Writer();
        getStr(in.nextLong());
    }
    
    String getStr(long n){
    	if(n==0) return "A";
    	long t = 1;
    	int len = 0;
    	while(n>=0){
    		len++;
    		t *= 26;
    		n -= t;
    	}
    	n += t;
    	String s = "";
    	for(int i=0; i<len; i++){
    		s = (char)(n%26+'A') + s;
    		n /= 26;
    	}
    	return s;
    }
}

class MultiSet<T> extends HashMap<T, Integer>{
	@Override
	public Integer get(Object key){return containsKey(key)?super.get(key):0;}
	public void add(T key,int v){put(key,get(key)+v);}
	public void add(T key){put(key,get(key)+1);}
	public void sub(T key){
		final int num = get(key);
		if(num==1) remove(key);
		else put(key, num-1);
	}
}
class Timer{
	long time;
	public void set(){time = System.currentTimeMillis();}
	public long stop(){return System.currentTimeMillis()-time;}
}
class Writer extends PrintWriter{
	public Writer(String filename) throws IOException
	{super(new BufferedWriter(new FileWriter(filename)));}
	public Writer() throws IOException{super(System.out);}
}
class ContestScanner {
	private BufferedReader reader;
	private String[] line;
	private int idx;
	public ContestScanner() throws FileNotFoundException 
	{reader = new BufferedReader(new InputStreamReader(System.in));}
	public ContestScanner(String filename) throws FileNotFoundException
	{reader = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));}
	public String nextToken() throws IOException {
		if (line == null || line.length <= idx) {
			line = reader.readLine().trim().split(" ");
			idx = 0;
		}
		return line[idx++];
	}
	public String readLine() throws IOException{return reader.readLine();}
	public long nextLong() throws IOException, NumberFormatException
	{return Long.parseLong(nextToken());}
	public int nextInt() throws NumberFormatException, IOException
	{return (int) nextLong();}
	public double nextDouble() throws NumberFormatException, IOException 
	{return Double.parseDouble(nextToken());}
}