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)

import sys
read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines

def main():
    S = readline().strip()
    T = readline().strip()

    seen = [0] * 26
    idx_in_S = []
    for t in T:
        ord_t = ord(t) - 97
        if seen[ord_t] == 0:
            t_idx = S.find(t) + 1
            if not t_idx:
                print(-1)
                exit()
            else:
                idx_in_S.append(t_idx)
                seen[ord_t] = t_idx
        else:
            begin = seen[ord_t]
            t_idx = S.find(t, begin) + 1
            if not t_idx:
                idx_in_S.append(seen[ord_t])
            else:
                idx_in_S.append(t_idx)
                seen[ord_t] = t_idx
    
    rep = 0
    for i in range(len(T) - 1):
        if idx_in_S[i] < idx_in_S[i+1]:
            continue
        else:
            rep += 1

    ans = len(S) * rep + idx_in_S[-1]
    print(ans)


if __name__ == "__main__":
    main()