import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.io.IOException; import java.io.BufferedReader; import java.io.Reader; import java.io.InputStreamReader; import java.io.InputStream; /** * 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; MyInput in = new MyInput(inputStream); PrintWriter out = new PrintWriter(outputStream); TaskD solver = new TaskD(); solver.solve(1, in, out); out.close(); } static class TaskD { public void solve(int testNumber, MyInput in, PrintWriter out) { int n = in.nextInt(); if (n == 1) { out.println("a"); return; } String ans = rec(n, 'a'); StringBuilder sb = new StringBuilder(ans); sb.reverse(); out.println(ans + sb.toString()); } String rec(int idx, char c) { if (c > 'z') c = 'a'; if (idx == 2) { return c + ""; } if (idx == 3) { return c + "" + (char) (c + 1); } if (idx % 2 == 1) { String s = rec(idx / 2, (char) (c + 1)); return c + "" + s.charAt(0) + s; } else { String s = rec(idx / 2, c); return s.charAt(0) + s; } } } static class MyInput { private final BufferedReader in; private static int pos; private static int readLen; private static final char[] buffer = new char[1024 * 8]; private static char[] str = new char[500 * 8 * 2]; private static boolean[] isDigit = new boolean[256]; private static boolean[] isSpace = new boolean[256]; private static boolean[] isLineSep = new boolean[256]; static { for (int i = 0; i < 10; i++) { isDigit['0' + i] = true; } isDigit['-'] = true; isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true; isLineSep['\r'] = isLineSep['\n'] = true; } public MyInput(InputStream is) { in = new BufferedReader(new InputStreamReader(is)); } public int read() { if (pos >= readLen) { pos = 0; try { readLen = in.read(buffer); } catch (IOException e) { throw new RuntimeException(); } if (readLen <= 0) { throw new MyInput.EndOfFileRuntimeException(); } } return buffer[pos++]; } public int nextInt() { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; int ret = 0; if (str[0] == '-') { i = 1; } for (; i < len; i++) ret = ret * 10 + str[i] - '0'; if (str[0] == '-') { ret = -ret; } return ret; } public char nextChar() { while (true) { final int c = read(); if (!isSpace[c]) { return (char) c; } } } int reads(int len, boolean[] accept) { try { while (true) { final int c = read(); if (accept[c]) { break; } if (str.length == len) { char[] rep = new char[str.length * 3 / 2]; System.arraycopy(str, 0, rep, 0, str.length); str = rep; } str[len++] = (char) c; } } catch (MyInput.EndOfFileRuntimeException e) { } return len; } static class EndOfFileRuntimeException extends RuntimeException { } } }