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: Accepted)

fun main(args : Array<String>) {
    val s = readLine()!!
    val t = readLine()!!

    val map = mutableMapOf<Char, MutableList<Long>>()

    s.forEachIndexed { index, c ->
        if (map.contains(c)) {
            map[c]!!.add(index.toLong())
        } else {
            map[c] = mutableListOf()
            map[c]!!.add(index.toLong())
        }
    }
    fun lowerBound(sortedList: List<Long>, key: Long) : Int {
        var ng = - 1 // left
        var ok = sortedList.size  // right

        fun isOk(mid: Int) : Boolean {
            return sortedList.get(mid) >= key
        }

        while (Math.abs(ok - ng) > 1) {
            var mid = (ok + ng) / 2
            if (isOk(mid)) {
                ok = mid
            } else {
                ng = mid
            }
        }
        return ok
    }

    // < O(logN)
    fun getNext(c: Char, current: Long) : Long {
        val indexes = map[c]
        if (indexes == null) {
            return -1
        }
        val key = current + 1
        val base = key / s.length
        val i = lowerBound(indexes, key)
        if (i >= indexes.size) {
            return indexes[0] + base * s.length.toLong() + s.length
        }
        return indexes[i] + base * s.length.toLong()
   }
   var current = 0L

    var ans = 0L
    var prev = -1L
   t.forEach {
       val indexes = map[it]
       if (indexes == null) {
           println(-1)
           return
       }
       val next = lowerBound(indexes, prev + 1)
       val nextIdx = if(next >= indexes.size) indexes.first() else indexes[next]
       ans += if(nextIdx > prev) nextIdx - prev else s.length - prev + nextIdx
       prev = nextIdx
   }
   println(ans)
}