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 Ruby (2.3.3) (judge verdict: Accepted)

s = gets.chomp
t = gets.chomp

len = s.length

i = 0
hash = {}
s.chars { |ch|
    if hash.key?(ch)
        hash[ch].push(i)
    else
        hash[ch] = [i]
    end
    i += 1
}

i = -1
t.chars { |ch|
    # print ch," ",i,"\n"
    if hash.key?(ch)
        list = hash[ch]
        pos = i%len

        if list.last <= pos
            i += len+list[0] - pos
        else
            head = 0
            tail = list.size-1
            mid = (head+tail)/2
            while head < tail
                if list[mid] <= pos
                    head = mid + 1
                else
                    tail = mid
                end
                mid = (head+tail)/2
            end
            i += list[mid] - pos
        end
    else
        i = -2
        break
    end
}

p i+1