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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

func Solve(stdin io.Reader, stdout io.Writer) {
	sc := bufio.NewScanner(stdin)

	/* 単語ごとに入力するならこれ */
	sc.Split(bufio.ScanWords)

	/* 入力バッファが大きくなるならこれ */
	buf := make([]byte, 1000000)
	sc.Buffer(buf, 1000000)

	sc.Scan()
	s := sc.Text()

	sc.Scan()
	t := sc.Text()

	list := make([][]int, 26)
	for i, v := range s {
		list[int(v - 'a')] = append(list[int(v - 'a')], i)
	}

	var cnt int64
	pos := -1

	for _, v := range t {
		vi := int(v - 'a')
		if len(list[vi]) == 0 {
			_, _ = fmt.Fprintf(stdout, "-1\n")
			return
		}
		done := false
		for _, x := range list[vi] {
			if x > pos {
				pos = x
				done = true
				break
			}
		}
		if !done {
			cnt++
			pos = -1
			for _, x := range list[vi] {
				if x > pos {
					pos = x
					done = true
					break
				}
			}
		}
	}

	fmt.Println(list)

	/* 出力用 */
	_, _ = fmt.Fprintf(stdout, "%v\n", int64(len(s)) * cnt + int64(pos) + 1)
}

func main() {
	Solve(os.Stdin, os.Stdout)
	return
}