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 Rust (1.15.1) (judge verdict: Wrong Answer)

use std::io::stdin;
use std::collections::HashMap;

fn main(){
    let input = || {
        let mut a = String::new();
        stdin().read_line(&mut a).unwrap();
        a.trim().to_string()
    };

    let s = input();
    let t = input();
    let mut pos = HashMap::<char, Vec<_>>::new();
    let mut current = 0;
    for tc in "abcdefghijklmnopqrstuvwxyz".chars() {
        pos.insert(tc, s.char_indices().filter_map(|(i, c)| if c == tc { Some(i) } else { None }).collect());
    }
    for tc in t.chars() {
        let scs = pos.get(&tc).unwrap();
        if scs.len() == 0{
            println!("-1");
            return;
        }
        let mut found = false;
        if let Err(i) = scs.binary_search(&((current % s.len()) + 1)) {
            if i < scs.len() {
                current += scs[i] - (current % s.len());
                found = true;
            }
        }
        if !found {
            current += s.len() - (current % s.len()) + scs[0];
        }
    }
    println!("{}", current + 1);
}