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 (1.3.71) (judge verdict: Accepted)

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

fun main() = abc138e()

@OptIn(ExperimentalStdlibApi::class)
fun abc138e() = SimpleFastIOWithToken_abc138e().exec {
    val s = readString()
    val t = readString()
    fun Char.toIndex() = this - 'a'

    val appearIndices = Array(26) { mutableListOf<Int>() }

    for ((index, sc) in s.repeat(2).withIndex()) {
        appearIndices[sc.toIndex()].add(index)
    }

    var currentIndex = s.lastIndex
    var answer = 0L

    for (tc in t) {
        val indices = appearIndices[tc.toIndex()]
        val nextIndex = indices.getOrNull(indices.upperBound(currentIndex)) ?: return@exec println(-1)
        answer += nextIndex - currentIndex
        currentIndex = nextIndex % s.length
    }

    println(answer)
}

// list must be sorted
private fun List<Int>.upperBound(key: Int): Int {
    var ng = -1
    var ok = size

    while (ok - ng > 1) {
        val mid = (ok + ng) / 2
        if (this[mid] > key) ok = mid else ng = mid
    }
    return ok
}

// region kokokara template dayo (^o^)
@Suppress("unused", "HasPlatformType", "MemberVisibilityCanBePrivate", "ClassName")
private class SimpleFastIOWithToken_abc138e(private val separator: String = System.lineSeparator()) {
    private val br: BufferedReader = System.`in`.bufferedReader()
    private var st: StringTokenizer = StringTokenizer("")
    private val sb: StringBuilder = StringBuilder()
    private fun prepareNext() = run { if (!st.hasMoreTokens()) st = StringTokenizer(br.readLine()) }

    fun readString(): String = run { prepareNext() }.run { st.nextToken() }
    fun readStringList(size: Int): List<String> = List(size) { readString() }
    fun readInt(): Int = Integer.valueOf(readString())
    fun readIntList(size: Int): List<Int> = List(size) { readInt() }
    fun readLong(): Long = java.lang.Long.valueOf(readString())
    fun readLongList(size: Int): List<Long> = List(size) { readLong() }
    inline fun <reified T> readArray(size: Int, init: () -> T) = Array(size) { init() }
    inline fun <T> readList(size: Int, init: () -> T) = List(size) { init() }

    fun println(): Unit = run { sb.append(separator) }
    fun print(any: Any): Unit = run { sb.append(any) }
    fun println(any: Any): Unit = print(any.toString() + separator)

    fun exec(action: SimpleFastIOWithToken_abc138e.() -> Unit) = run {
        Thread(null, { action() }, "(^o^)", 128 * 1024 * 1024).apply { start() }.join()
    }.run { kotlin.io.print(sb) }

    fun readLine(): Nothing = error("readLine is disabled.")
}
// endregion kokomade template dayo (^o^)