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 Scala (2.11.7) (judge verdict: Runtime Error)

object Main {

  import scala.collection.mutable.ArrayBuffer

  def main(args: Array[String]): Unit = {
    val sc = new java.util.Scanner(System.in)

    val S, T = sc.nextLine()
    var IDX = Array.fill(26)(ArrayBuffer[Long]())

    var i = 0
    while (i < S.length) {
      IDX(S(i) - 'a').append(i)
      i += 1
    }
    IDX = IDX.map { arr =>
      arr ++ arr.map(_ + S.length.toLong)
    }

    def lowerBound(arr: IndexedSeq[Long], x: Long): Int = {
      def dfs(l: Int, r: Int): Int =
        if (r - l > 1) {
          val center = l + (r - l) / 2
          if (arr(center) <= x) dfs(center, r)
          else dfs(l, center)
        } else r
      dfs(-1, arr.length)
    }

    i = 0
    var round = 0L
    var j = -1L
    while (i < T.length) {
      val IDX_T = IDX(T(i) - 'a')
      var idxT = lowerBound(IDX_T, j)
      if (idxT == IDX_T.length) {
        if (j == 0) {
          println("-1")
          return
        }
        round += 1L
        j = IDX_T(lowerBound(IDX_T, -1L))
      } else {
        j = IDX_T(idxT)
      }
      i += 1
    }
    println(2L * round * S.length.toLong + (j + 1L))
  }

}