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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

import java.util.HashMap
fun main(args: Array<String>) {
    val S = readLine()!!
    val T = readLine()!!
    val SL = S.length
    val TL = T.length
    val M = hashMapOf<Char, MutableList<Int>>()
    S.forEachIndexed{ index, char ->
        val e = M[char]
        if (e == null) M.put(char, mutableListOf(index, index + SL)) else e.addAll(listOf(index, index + SL))
    }
    for ((k, v) in M) v.sort()
    var sn = 0
    var tn = 0
    while (tn < TL) {
        val e = M[T[tn]]
        if (e == null) {
            println(-1)
            return //exit
        }
        val b = e.binarySearch(sn % SL)
        val p = if (b < 0) e[b.inv()] else e[b]
        sn += (p - sn % SL + 1)
        tn += 1
    }
    println(sn)
}