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
a = Array.new(26){Array.new(0)}

for i in 0...S.size do
    a[S[i].ord-97].push(i)
end

T = gets.chomp
b = 0
c = -1
s = 0
for i in 0...T.size do
    s = T[i].ord-97
    if a[s].empty?
        puts "-1"
        exit
    elsif a[s].last > c
        if a[s][0] > c
            c = a[s][0]
        else
            l = 0
            r = a[s].size-1
            o = (l+r)/2
            while r-l > 1
                if a[s][o] > c
                    r = o
                else
                    l = o
                end
                o = (l+r)/2
            end
            c = a[s][r]
        end
    else
        b += 1
        c = a[s][0]
    end
end
answer = (b*S.size)+c+1
puts answer