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 Python (3.4.3) (judge verdict: Wrong Answer)

# -*- coding: utf-8 -*-


def main():
    from bisect import bisect_right

    s = input()
    t = input()
    n = len(s)
    m = len(t)
    alpha = [[] for _ in range(26)]

    # KeyInsight
    # 部分列判定：場所i以降で文字Cが最初に現れる位置を高速に求める
    # アルファベットの出現位置をリストで記録

    # sで各文字が出現する位置を2周分記録
    for index, si in enumerate(s):
        alpha[(ord(si) - ord('a'))].append(index)

    for index, si in enumerate(s):
        alpha[(ord(si) - ord('a'))].append(index + n)

    ans = 1
    p = 0

    for ti in t:
        c = ord(ti) - ord('a')

        if len(alpha[c]) == 0:
            print('-1')
            exit()

        p = alpha[c][bisect_right(alpha[c], p)]

        if p >= n:
            p -= n
            ans += n

    ans += p

    print(ans)


if __name__ == '__main__':
    main()