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: Runtime Error)

package main

import (
	"fmt"
	"bufio"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)
func scanInt() int {
	sc.Scan()
	a,_ := strconv.Atoi(sc.Text())
	return a
}

func scanText() string {
	sc.Scan()
	return sc.Text()
}

func main() {
	sc.Split(bufio.ScanWords)
	
	s,t := scanText(),scanText()

	next := make([][]int, len(s)+1)
	for i := 0; i < len(s)+1; i++ {
		next[i] = make([]int, 26)
	}
	
	for i := len(s)-1; i >= 0; i-- {
		for j := 0; j < 26; j++ {
			next[i][j] = next[i+1][j]
		}
		next[i][s[i]-'a'] = i+1
	}

	ans := int64(0)
	for i := 0; i < len(t); i++ {
		x := int64(next[ans%int64(len(s))][t[i]-'a'])
		if x != 0 {
			ans += x - ans%int64(len(s))
		} else {
			x0 := int64(next[0][t[i]-'a'])
			if x0 != 0 {
				ans += x0 + int64(len(s)) - ans%int64(len(s))
			} else {
				fmt.Println(-1)
				return
			}
		}
	}

	fmt.Println(ans)

}