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: Accepted)

-- https://github.com/minoki/my-atcoder-solutions
{-# LANGUAGE BangPatterns #-}
import Data.Int (Int64)
import qualified Data.Vector as V
import qualified Data.ByteString.Char8 as BS
import Data.Array.Unboxed

buildTable :: BS.ByteString -> V.Vector (UArray Char Int)
buildTable s = let s' = V.generate (BS.length s) $ \i -> BS.index s i
               in V.scanr (\(i,c) a -> a // [(c,i)]) (array ('a','z') [(c,-1) | c <- ['a'..'z']]) (V.indexed s')

main = do
  s <- BS.getLine
  t <- BS.getLine
  let s_table = buildTable s
  let loop :: Int64 -> Int -> BS.ByteString -> Int64
      loop !i !j t = case BS.uncons t of
                       Nothing -> i
                       Just (c, t') ->
                         let k = (s_table V.! j) ! c
                         in if k == -1
                            then let l = V.head s_table ! c
                                 in if l == -1
                                    then -1
                                    else loop (i + fromIntegral (l + BS.length s - j) + 1) (l+1) t'
                            else loop (i + fromIntegral (k - j) + 1) (k+1) t'
  print $ loop 0 0 t