统计数字字符个数

{
  "problem": {
    "name": "统计数字字符个数",
    "description": {
      "content": "输入一行字符，统计出其中数字字符的个数。",
      "description_type": "Markdown"
    },
    "platform": "Luogu",
    "limit": {
      "time_limit": 1000,
      "memory_limit": 131072
    },
    "difficulty": {
      "LuoguStyle": "P1"
    },
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "LGB2109"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "输入一行字符，统计出其中数字字符的个数。\n\n## Input\n\n一行字符串，总长度不超过 $255$。\n\n## Output\n\n输出为 $1$ 行，输出字符串里面数字字符的个数。\n\n[samples]...",
      "is_translate": false,
      "language": "English"
    }
  ]
}