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.io.InputStreamReader
import java.io.PrintWriter

val br = BufferedReader(InputStreamReader(System.`in`))
val out = PrintWriter(System.out)

fun main() {
    br.use { out.use {
        solve()
        out.flush()
    } }
}

fun solve() {
    val s = br.readLine()!!
    val t = br.readLine()!!

    val sSet = s.toSet()
    if (sSet.union(t.toSet()).size > sSet.size) {
        out.println(-1)
        return
    }

    val charOccurenceList = Array('z' - 'a' + 1) { mutableListOf<Int>() }
    for ((i, c) in s.withIndex()) {
        charOccurenceList[c - 'a'].add(i + 1)
    }

    var ans = 0L
    var preIndex = 0
    for (c in t) {
        var left = -1
        var right = charOccurenceList[c - 'a'].size
        while (right - left > 1) {
            val mid = (left + right) / 2
            if (preIndex < charOccurenceList[c - 'a'][mid]) {
                right = mid
            } else {
                left = mid
            }
        }

        if (right !in charOccurenceList[c - 'a'].indices) {
            val nextIndex = charOccurenceList[c - 'a'][0]
            ans += s.length - preIndex + nextIndex
            preIndex = nextIndex
        } else {
            val nextIndex = charOccurenceList[c - 'a'][right]
            ans += nextIndex - preIndex
            preIndex = nextIndex
        }
    }

    out.println(ans)
}

fun readInteger() = Integer.parseInt(br.readLine())
fun readLong() = java.lang.Long.parseLong(br.readLine())
fun readStringList() = br.readLine()!!.split(' ')
fun readIntegerList() = readStringList().map(Integer::parseInt)
fun readLongList() = readStringList().map(java.lang.Long::parseLong)
fun readDoubleList() = readStringList().map(java.lang.Double::parseDouble)