Problem:
Score : 500 points

Problem Statement

Given are two strings s and t consisting of lowercase English letters. Determine if there exists an integer i satisfying the following condition, and find the minimum such i if it exists.

Let s' be the concatenation of 10^{100} copies of s. t is a subsequence of the string {s'}_1{s'}_2\ldots{s'}_i (the first i characters in s').

Notes

A subsequence of a string a is a string obtained by deleting zero or more characters from a and concatenating the remaining characters without changing the relative order. For example, the subsequences of contest include net, c, and contest.

Constraints

1 \leq |s| \leq 10^5

1 \leq |t| \leq 10^5

s and t consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s
t

Output

If there exists an integer i satisfying the following condition, print the minimum such i; otherwise, print -1.

Sample Input 1

contest
son

Sample Output 1

10

t = son is a subsequence of the string contestcon (the first 10 characters in s' = contestcontestcontest...), so i = 10 satisfies the condition.

On the other hand, t is not a subsequence of the string contestco (the first 9 characters in s'), so i = 9 does not satisfy the condition.

Similarly, any integer less than 9 does not satisfy the condition, either. Thus, the minimum integer i satisfying the condition is 10.

Sample Input 2

contest
programming

Sample Output 2

-1

t = programming is not a substring of s' = contestcontestcontest.... Thus, there is no integer i satisfying the condition.

Sample Input 3

contest
sentence

Sample Output 3

33

Note that the answer may not fit into a 32-bit integer type, though we cannot put such a case here.

Solution in Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

{-# OPTIONS_GHC -O2 #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE BangPatterns #-}
module Main where

import Control.Arrow
import Control.Monad
import Control.Monad.ST
import Control.Monad.State.Strict
import Data.Char
import Data.Function
import Data.Graph
import Data.List
import Data.Maybe
import qualified Data.Vector as V
import qualified Data.Vector.Mutable as VM
import qualified Data.Vector.Unboxed as U
import qualified Data.Vector.Unboxed.Mutable as UM
import qualified Data.ByteString.Char8 as C
import qualified Data.ByteString.Unsafe as B
import qualified Data.ByteString.Builder as BSB
import System.IO (stdout)

type Parser a = C.ByteString -> Maybe (a, C.ByteString)

parseInt :: Parser Int
parseInt = C.readInt . C.dropWhile isSpace

parseInt2 :: Parser (Int, Int)
parseInt2 = runStateT $
    (,) <$> StateT (C.readInt . C.dropWhile isSpace)
        <*> StateT (C.readInt . B.unsafeTail)
 
parseInt3 :: Parser (Int, Int, Int)
parseInt3 = runStateT $
    (,,) <$> StateT (C.readInt . C.dropWhile isSpace)
        <*> StateT (C.readInt . B.unsafeTail)
        <*> StateT (C.readInt . B.unsafeTail)
 
parseInt4 :: Parser (Int, Int, Int, Int)
parseInt4 = runStateT $
    (,,,) <$> StateT (C.readInt . C.dropWhile isSpace)
        <*> StateT (C.readInt . B.unsafeTail)
        <*> StateT (C.readInt . B.unsafeTail)
        <*> StateT (C.readInt . B.unsafeTail)

-- prime means pred
parseInt' :: Parser Int
parseInt' = fmap (pred *** id) . parseInt

getInts :: IO [Int]
getInts = unfoldr parseInt <$> C.getLine

-- prime means pred
getInts' :: IO [Int]
getInts' = unfoldr parseInt' <$> C.getLine

getIntTuple :: IO (Int, Int)
getIntTuple = do
  a:b:_ <- getInts
  return (a, b)

-- prime means pred
getIntTuple' :: IO (Int, Int)
getIntTuple' = do
  a:b:_ <- getInts'
  return (a, b)

getIntTuple3 :: IO (Int, Int, Int)
getIntTuple3 = do
  a:b:c:_ <- getInts
  return (a, b, c)

getIntTuple4 :: IO (Int, Int, Int, Int)
getIntTuple4 = do
  a:b:c:d:_ <- getInts
  return (a, b, c, d)

getIntVec :: Int -> IO (U.Vector Int)
getIntVec n = U.unfoldrN n parseInt <$> C.getLine

-- prime means pred
getIntVec' :: Int -> IO (U.Vector Int)
getIntVec' n = U.unfoldrN n parseInt' <$> C.getLine

---------------------------------------------------------

main :: IO ()
main = do
  s <- C.getLine
  t <- C.getLine
  print (match s t (C.length s) 0 0)


type Count = Integer
type Length = Int
type Index = Int

match :: C.ByteString -> C.ByteString -> Length -> Index -> Count -> Count
match s !t !l !i !c | C.null t = c
                    | c >  lim = -1
                    | C.index s i == C.head t = match s (C.tail t) l ((i+1) `mod` l) (c+1)
                    | otherwise               = match s t          l ((i+1) `mod` l) (c+1)
  where
    lim :: Integer
    lim = fromIntegral (l*(10^100))