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 8.8.3) (judge verdict: Accepted)

import Data.IntSet (IntSet)
import qualified Data.IntSet as IS
import qualified Data.Vector as V

main :: IO ()
main = do
  s <- map (subtract (fromEnum 'a') . fromEnum) <$> getLine :: IO [Int]
  let
    l = length s :: Int
    sSets = V.accum (flip IS.insert) (V.replicate 26 IS.empty) . flip zip [0..] $ s :: V.Vector IntSet
    f :: [Int] -> Maybe (Int, Maybe Int)
    f = foldl step Nothing
      where
        step :: Maybe (Int, Maybe Int) -> Int -> Maybe (Int, Maybe Int)
        step Nothing x = Just (0, IS.lookupGE 0 (sSets V.! x))
        step (Just (i, Just j)) x | Nothing <- m = Just (i + 1, IS.lookupGE 0 (sSets V.! x))
                                  | otherwise    = Just (i, m)
          where
            m = IS.lookupGT j (sSets V.! x)
        step _ _ = Just (0, Nothing)
    g :: Maybe (Int, Maybe Int) -> Int
    g (Just (i, Just j)) = l * i + j + 1
    g _                  = -1
  t <- map (subtract (fromEnum 'a') . fromEnum) <$> getLine :: IO [Int]
  print . g . f $ t