# [QBIC](https://drive.google.com/drive/folders/0B0R1Jgqp8Gg4cVJCZkRkdEthZDQ), 31 bytes

    ~:>:|≈:-a>0|q=q+1┘c=c-a+b]?q\?0

##Explanation

    ~           IF
     :          cmd line arg 'a'  (the increment of our snail)
      >         is greater than
       :        cmd line arg 'b'  (the decrement, or daily drop)
        |       THEN
    ≈           WHILE
     :          cmd line arg 'c'  (the height of the well)
      -a        minus the increment (we count down the hieght-to-go)
        >0|     is greater than 0 (ie while we haven't reached the top yet)
    q=q+1       Add a day to q (day counter, starts at 1)
    ┘           (syntactic linebreak)
    c=c-a+b     Do the raise-and-drop on the height-to-go
    ]           WEND
    ?q          PRINT q (the number of days)
    \?0         ELSE (incrementer <= decrementer) print 0 (no solution)

[Try it online!](https://repl.it/JRcM/1) (OK, not really: this is a translation of QBIC to QBasic code run in repl.it 's (somewhat lacking) QBasic enviroment)