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)

#!/usr/bin/env python3
import sys
from bisect import bisect_left
from collections import defaultdict
INF = float("inf")


def solve(s: str, t: str):

    S = len(s)
    T = len(t)
    ABC = defaultdict(list)
    for i, c in enumerate(s):
        ABC[c].append(i)

    counter = 0
    head = 0
    # print(ABC)
    for tt in t:
        if len(ABC[tt]) == 0:
            print(-1)
            return
        j = bisect_left(ABC[tt], head) % len(ABC[tt])
        # print(tt, ABC[tt], j, ABC[tt][j], head)
        counter += (ABC[tt][j]-head+1) % S
        head = (ABC[tt][j]+1) % S
    print(counter)
    return


def main():

    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    s = next(tokens)  # type: str
    t = next(tokens)  # type: str
    solve(s, t)


if __name__ == '__main__':
    main()