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)

from array import array
from collections import deque

#sys.setrecursionlimit(200000)

import sys

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

s = input()
t = input()


# find Longest common subsequence
# returns indexes of last common char in s1 and s2
def find_lcs(s1,s2):
    s2array = array('u', s2)
    i_s1 = -1
    i_s2 = 0
    for i,c in enumerate(s1):
        if i_s2 > len(s2)-1:
            break
        if c == s2array[i_s2]:
            i_s1 = i # current index in s1
            i_s2 += 1 # next index in s2
    return i_s1, i_s2-1

count = 0

i_sdash = 0
i_t = 0
ttail = t[0:]

while True:
    i,j = find_lcs(s,ttail)
    ttail = ttail[j+1:]
    if i == -1 and i_sdash == 0:
        print(-1)
        sys.exit()
    elif i == -1 and i_sdash > 0:
        break
    else:
        i_sdash = len(s)*count + i
        count += 1

print(i_sdash+1)