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 (2.4.0) (judge verdict: Accepted)

s = input()
t = input()
d = {i:[] for i in "abcdefghijklmnopqrstuvwxyz"}
for i in range(len(s)):
    d[s[i]].append(i)
for i in t:
    if len(d[i]) == 0:
        print(-1)
        exit()

def binary_search(arr, k):
    l, r = 0, len(arr)-1
    while l <= r:
        m = l+r >> 1
        if arr[m] < k:
            l = m+1
        else:
            r = m-1
    return l

a, b = 0, 0
for i in t:
    j = binary_search(d[i], a)
    if len(d[i]) <= j:
        a = 0
        b += 1
        j = binary_search(d[i], 0)
    a = d[i][j] + 1
print(b * len(s) + a)