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: Accepted)

package main

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

var sc *bufio.Scanner

const BufferSize = 1024

func nextString() string {
	if !sc.Scan() {
		panic(nil)
	}
	return sc.Text()
}

var production bool

func debugf(format string, v ...interface{}) {
	if !production {
		fmt.Printf(format, v...)
	}
}

func answer(reader io.Reader, writer io.Writer) {
	sc = bufio.NewScanner(reader)
	buf := make([]byte, BufferSize)
	sc.Buffer(buf, 1e+6)
	sc.Split(bufio.ScanWords)
	s := nextString()
	t := nextString()

	si := make([][]int, 26)
	for i := range s {
		a := rune(s[i]) - rune(`a`[0])
		si[a] = append(si[a], i+1)
	}
	debugf("%v\n", si)

	ans := uint64(0)
	idx := 0
	for i := range t {
		a := rune(t[i]) - rune(`a`[0])
		if len(si[a]) == 0 {
			_, _ = fmt.Fprint(writer, "-1")
			return
		}
		k := sort.Search(len(si[a]), func(k int) bool { return idx < si[a][k] })
		debugf("find: %s, idx: %d, k: %d from %v\n", string(t[i]), idx, k, si[a])
		/*
			j := 0
			for si[a][j] <= idx {
				if j == len(si[a])-1 {
					idx = 0
					ans += uint64(len(s))
					debugf("reset: %s, %d, %d\n", string(t[i]), idx, ans)
					j = 0
					break
				}
				j++
			}
			idx = si[a][j]
		*/
		if k == len(si[a]) {
			idx = 0
			ans += uint64(len(s))
			k = 0
		}
		idx = si[a][k]
		debugf("index: %s, %d\n", string(t[i]), idx)
	}

	_, _ = fmt.Fprintf(writer, "%d", ans+uint64(idx))
}

func main() {
	production = true
	answer(os.Stdin, os.Stdout)
}