#include <stdio.h>

void
put (int n)
{
  putchar ('`' + n);
}

void
doit (int n)
{
  int i;

  put (n);
  put (n);

  if (n == 1) return;

  doit (n - 1);

  for (i = 1; i < n - 1; ++i)
    put (n), put (i);

  put (n);
}

int
main (int argc, char *argv[])
{
  doit (atoi (argv[1]));
  putchar ('\n');
  return 0;
}