[{"_1":2,"_3":-5,"_4":-5},"loaderData",{"_5":6,"_7":8,"_9":10,"_11":12,"_13":14},"actionData","errors","root",{"_124":125,"_126":117},"routes/_root/_root",{"_119":-7,"_120":121,"_122":-7,"_123":-7},"routes/_root.challenges",{"_114":115,"_116":117,"_118":18},"routes/_root.challenges.$challengeCanonical+/_root",{"_36":37,"_38":39,"_40":41},"routes/_root.challenges.$challengeCanonical+/solves",{"_15":16,"_17":18,"_19":18,"_20":21,"_22":-5},"solves",[23,24],"isCtf",false,"isMirror","entityLabel","USER","ctfScopedSolvesNotice",{"_25":32,"_27":33,"_29":34,"_30":35},{"_25":26,"_27":28,"_29":-5,"_30":31},"name","umineko","href","/users/umineko","gravatarHash","createdAt",["D",1784109743209],"nakamulab","/users/nakamulab","8715bf5f88ebc6a7c61522af8a26fe21471cef0a706cb24f1e28799767bf577a",["D",1784304314589],"challenge",{"_25":45,"_46":47,"_15":48,"_49":50,"_51":52,"_53":54,"_55":56,"_57":58,"_59":60,"_61":62,"_63":18,"_64":-7,"_65":66,"_67":-7,"_68":-7,"_69":18,"_70":71,"_72":73,"_74":18,"_75":-7,"_76":18,"_77":-7,"_78":-7,"_79":-7,"_19":-7,"_80":-7,"_81":-7,"_82":18,"_83":18,"_84":85,"_86":85,"_87":18,"_88":-7,"_89":-7,"_90":-7,"_91":-7,"_92":93},"availablePages",[42,43,44],"canonicalUrl","https://alpacahack.com/challenges/lean-as-a-service","Description","Solves","Writeups","Lean as a Service","canonicalName","lean-as-a-service",2,"difficulty",45,"flagFormat","Alpaca{...}","categories",[111],"attachments",[106],"remote",{"_103":104,"_105":85},"description","I made a web service where you can easily play with the trendy Lean!\nIt only verifies proofs, so you can't do anything bad to the server, right?\n\n

Beginner Hint

\n\n- The flag is stored in `/flag-.txt`. Your goal is to read it.\n- Lean is a theorem prover, but it is also a functional programming language. In particular, Lean 4 has stronger support for general-purpose programming.\n- Try researching how to execute OS commands in Lean.\n\n

\n","descriptionJa","流行りの Lean を簡単に遊べる Web サービスを作りました！ \n証明を検証するだけだから、サーバーに悪さなんてできないよね？\n\n

初心者向けヒント

\n\n- フラグは `/flag-.txt` に保存されています。これを読み取るのがゴールです。\n- Lean は定理証明支援系であると同時に、関数型プログラミング言語でもあります。特に Lean 4 では、汎用プログラミングの側面が強化されています。\n- Lean でどう OS コマンドを実行できるかを調査してみましょう。\n\n

\n","descriptionRequiresSignIn","changeLog","authors",[100],"solvedAt","solvedAtInContext","likedByViewer","ctfChallenges",[],"tags",[94,95],"submitAsCtfChallenge","ctfCanonical","ctfEnded","point","solvesCtfChallenge","classification","ctfParticipants","ctfMode","isDailyChallenge","canCheckFlagWithoutSubmission","canCreateInstance",true,"canLike","showcaseMode","dailyProgramCanonicalForAction","reviewProgramCanonicalForAction","dailyChallengeSlot","nextDailyCanonical","httpsProxyHostname","lean-as-a-service.chal.alp4ca.com",{"_25":98,"_46":99},{"_25":96,"_46":97},"Jail","jail","Lean","lean",{"_25":101,"_29":102},"minaminao","8923101afaa06c6be81216763685dbd0cac8ff24fbd6646250f67608d4924b02","instances",[],"canSpawn",{"_107":108,"_109":110},"fileName","lean-as-a-service.tar.gz","url","https://alpacahack-prod.s3.ap-northeast-1.amazonaws.com/8d116d86-29fe-45c3-b1a2-0692fef0bf8f/lean-as-a-service.tar.gz",{"_25":112,"_46":113},"Misc","misc","title","Challenges","query","","isLoggedIn","user","language","en","timeZone","timeZoneAbbr","clientConfig",{"_127":128,"_129":85,"_130":131,"_132":131,"_133":134,"_135":136,"_137":18,"_138":117},"cspNonce","firebaseOptions",{"_139":140,"_141":142,"_143":144,"_145":146,"_147":148,"_149":134},"isVercel","env","production","envName","gaTrackingId","G-FJX5L5Y9FE","turnstileSiteKey","0x4AAAAAAAfYTP7SUci3nVKW","isSpawnerUnderMaintenance","spawnerMaintenanceNotice","apiKey","AIzaSyDGInmUCFubPOqJWQCw3LBB-XZGj9LX4l4","appId","1:691353492123:web:4ae258ec8c620e63f0443e","projectId","alpacahack","authDomain","alpacahack.firebaseapp.com","messagingSenderId","691353492123","measurementId"]

USER	SOLVED AT
nakamulab	11 hours ago
umineko	2026/07/15 10:02