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       "21124"
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   "source": [
    "special_cases = {1: \"one\", 2: \"two\", 3: \"three\", 4: \"four\", 5: \"five\", 6: \"six\", 7: \"seven\", 8: \"eight\", 9: \"nine\",\n",
    "                 10: \"ten\", 11: \"eleven\", 12: \"twelve\", 13: \"thirteen\",  15: \"fifteen\", 18: \"eighteen\",\n",
    "                 20: \"twenty\", 30: \"thirty\", 40: \"forty\", 50: \"fifty\", 60: \"sixty\", 70: \"seventy\", 80: \"eighty\",\n",
    "                 90: \"ninety\"}\n",
    "\n",
    "\n",
    "def number_to_words(n):\n",
    "    assert n <= 1000\n",
    "    if special_cases.get(n):\n",
    "        return special_cases[n]\n",
    "    if 14 <= n <= 19:\n",
    "        return special_cases[n % 10] + \"teen\"\n",
    "    if 20 <= n <= 99:\n",
    "        return special_cases[n // 10 * 10] + \"-\" + special_cases[n % 10]\n",
    "    if 100 <= n <= 999:\n",
    "        if n % 100 == 0:\n",
    "            return special_cases[n // 100] + \" \" + \"hundred\"\n",
    "        return special_cases[n // 100] + \" \" + \"hundred and \" + number_to_words(n % 100)\n",
    "    if n == 1000:\n",
    "        return \"one thousand\"\n",
    "\n",
    "\n",
    "all_numbers = \"\"\n",
    "for i in range(1, 1000+1):\n",
    "    all_numbers += number_to_words(i)\n",
    "all_numbers = all_numbers.replace('-', '')\n",
    "all_numbers = all_numbers.replace(' ', '')\n",
    "len(all_numbers)"
   ]
  }
 ],
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  "title": "Number letter counts"
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