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: Runtime Error)

import sys
from collections import defaultdict

def bs(arr, val):
	l, h = 0, len(arr)-1
	ans = -1
	while l <= h:
		m = l + h >> 1
		if arr[m] > val:
			ans = m
			h = m - 1
		else:
			l = m + 1
	return ans

s = sys.stdin.readline()
n = len(s)

t = sys.stdin.readline()

occurence = defaultdict(list)
for i in range(n):
	occurence[s[i]].append(i+1)

folds = 0
cur_ptr = 0
for ele in t:
	indexes = occurence[ele]
	idx = bs(indexes, cur_ptr)
	if idx != -1: 
		cur_ptr = indexes[idx]
	else:
		folds += 1
		cur_ptr = indexes[0]
ans = folds*(n) + cur_ptr
print(ans)