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: Time Limit Exceeded)

import java.io.*
import java.util.*

const val A = 97
fun solve(s: String, t: String) {
    val indices = Array(26) { mutableListOf<Int>() }
    s.withIndex().forEach {
        indices[it.value.toInt() - A].add(it.index)
    }
    // println(indices)
    var ans = 0L
    var ret = 0
    for (chr in t) {
        // println(ans)
        val idx = indices[chr.toInt() - A]
        if (idx.size == 0) { println(-1); return }
        val M = idx.max()!!
        if (M < ret) {
            ans += s.length - ret + idx.min()!! +1
            ret = idx.min()!! + 1
        } else if (M == ret) {
            ret++
            ans++
        }
        else{
            // retを超える最小のidx
            val insertPos = idx.binarySearch(ret)
            val pos = when {
                insertPos < 0 -> - insertPos - 1
                else -> insertPos
            }
            ans += idx[pos] - ret + 1
            ret = idx[pos] + 1
        }
    }
    println(ans)
    return
}

fun main(args: Array<String>) {
    fun StringArray(size: Int, init: (Int) -> String = { "\u0000" }): Array<String> {
        return Array<String>(size, init)
    }
    class Scanner(stream: InputStream) {
        private val reader = BufferedInputStream(stream).bufferedReader()
        private var st: StringTokenizer? = null
        fun next(): String {
            while (!(st?.hasMoreTokens() ?: false)) st = StringTokenizer(reader.readLine())
            return st!!.nextToken()
        }
    }
    val sc = Scanner(System.`in`)
    val s = sc.next()
    val t = sc.next()
    solve(s, t)
}