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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        
        char s[] = str1.toCharArray();
        char t[] = str2.toCharArray();
        int n = s.length;
        int m = t.length;
        
        // set: 英小文字の出現位置
        TreeSet[] set = new TreeSet[26];
        for (int i = 0; i < 26; i++) {
            set[i] = new TreeSet<Integer>();
        }
        
        // 2周分覚える
        // contestcontest -> set[c] = {0, 7}
        for (int i = 0; i < n; i++) {
            char c = s[i];
            set[c - 'a'].add(i);
        }
        for (int i = 0; i < n; i++) {
            char c = s[i];
            set[c - 'a'].add(i + n);
        }
        
        // ans: 文字列tの各文字の文字列sにおける出現位置を足したもの
        // ex. (s, t) = (contest, son) => ans = 6 + 3 + 1 = 10
        int ans = 1;
        int now = 0;
        for (int i = 0; i < m; i++) {
            char c = t[i];
            if (set[c - 'a'].size() == 0) {
                System.out.println(-1);
                return;
            }
            
            // 文字cのnow文字目以降で最も早い出現位置を代入
            // 進んだ距離を足す
            int next = (int)set[c - 'a'].higher(now);
            ans += (next - now);
            
            // 次の周に行く場合無駄にn多くなるので減算
            if (next >= n) {
                next -= n;
            }
            now = next;
        }
        System.out.println(ans);
    }
}