import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.io.OutputStream;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
import java.util.ArrayList;
import java.util.List;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long N = in.nextLong();
            long c;
            int keta=0;
            long num=1;
            long[] ans = new long[10];
            int m = 0;
            while(N!=0){
                num=1;
                keta=0;
                c = N;
                if(c==26){
                    ans[1] = 1;
                    keta=1;
                    m = Math.max(m,keta);
                    break;
                }
                while(c>0){
                    if(c<=26){
                        num = num*c;
                        break;
                    }
                    c = c/26;
                    keta++;
                    num = num*26;
                }
                m = Math.max(m,keta);
                ans[keta] = c;
                N = N-num;
            }
            for(int i=m; i>=1; i--){
                out.print((char)('A'+ans[i]-1));
            }
            out.println((char)('A'+ans[0]));
        }
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }
}