(def input
  [53247
   140268
   139961
   87816
   102986
   122415
   140484
   56099
   52832
   56999
   122823
   130608
   83149
   144224
   104559
   108523
   126571
   137284
   83197
   109996
   56795
   73112
   50043
   130097
   113563
   91200
   130589
   83725
   108625
   131977
   95213
   149800
   70756
   86240
   134854
   148919
   114460
   95062
   122989
   57274
   112074
   139530
   131217
   55652
   125522
   77304
   144873
   86811
   107768
   70704
   146300
   87256
   118752
   52585
   126269
   124559
   52592
   112097
   123090
   101778
   136424
   74547
   119337
   143570
   113426
   146458
   88135
   100236
   148224
   98718
   135181
   56608
   109671
   144027
   135192
   111620
   69411
   107957
   88448
   64972
   63010
   100625
   96144
   61998
   59813
   124503
   64306
   73119
   77094
   136295
   132224
   125713
   110137
   51478
   90272
   133506
   72218
   100082
   106377
   140290])

(defn required-fuel [mass]
  (- (int (Math/floor (/ mass 3))) 2))

(->> input
     (map required-fuel)
     (reduce + 0)) ;; => 3452245