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 PyPy3 (7.3.0) (judge verdict: Accepted)

import sys
import bisect

# \n
def input():
    return sys.stdin.readline().rstrip()


def main():
    S = list(input())
    T =list(input())

    G =[[] for _ in range(26)]

    orda =ord("a")

    for i in range(len(S)):
        G[ord(S[i])-orda].append(i)

    count =0
    p=-1
    for j in range(len(T)):
        tord = ord(T[j]) -orda
        if G[tord]!=[]:
            if G[tord][-1]<p+1:
                p=-1
                count+=1

            gp =bisect.bisect_left(G[tord],p+1)
            p =G[tord][gp]

        else:
            print(-1)
            exit()


    print(count * len(S)+p+1)





if __name__ == "__main__":
    main()