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 OCaml (4.02.3) (judge verdict: Wrong Answer)

let s = read_line ()
let t = read_line ()

let s_len = String.length s
let t_len = String.length t

let ch_pos =
  let ss = s ^ s in
  let len = s_len * 2 in
  let rec f arr i =
    if i = -1 then arr
    else begin
      arr.(i) <- Array.copy arr.(i + 1);
      arr.(i).(int_of_char ss.[i] - int_of_char 'a') <- i;
      f arr (i - 1)
    end
  in
  f (Array.init (len + 1) (fun _ -> Array.make 26 (-1))) (len - 1)

let rec loop sum i pos =
  if i = t_len then
    print_int sum
  else 
    let next = ch_pos.(pos).(int_of_char t.[i] - int_of_char 'a') in
    if next = -1 then begin
      print_int (-1); exit 0;
    end else loop (sum + next - pos) (i + 1) (next mod s_len)

let () = loop 1 0 0