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: Accepted)

import collections

s = input()
t = input()
s_len = len(s)
s_idx = dict([])
for i, key in enumerate(s):
    try:
        s_idx[key].append(i + 1)
    except KeyError:
        s_idx[key] = [i + 1]

def binary_search(li, tmp, ng, ok):
    mid = (ng + ok) // 2
    if ok - ng < 2:
        if ok == len(li):
            return s_len + li[0]
        else:
            return li[ok]
    if li[mid] <= tmp: return binary_search(li, tmp, mid, ok)
    else: return binary_search(li, tmp, ng, mid)

ans = 0
ex_i = 0
for key in t:
    try:
        i = binary_search(s_idx[key], ex_i, -1, len(s_idx[key]))
        ans += i - ex_i
        ex_i = i % s_len
    except KeyError:
        ans = -1
        break
print(ans)