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)

fn main() {
    let s = read::<String>();
    let t = read::<String>();

    // どの文字が何番目にあるかのリスト。list[0]はaが何文字目に出るかのリスト
    let mut list: Vec<Vec<usize>> = vec![vec![]; 26];

    let mut ans: isize = 0;

    let len_s = s.len();

    // リストの作成(昇順になる)
    for (e, c) in s.chars().enumerate() {
        list[(c as i32 - 0x61) as usize].push(e)
    }

    let mut prev_pos: isize = -1;
    let mut flg = false; // 直前に次のsに入ったか

    for c in t.chars() {
        let l = &list[(c as i32 - 0x61) as usize];
        if l.is_empty() == true {
            println!("-1");
            return;
        }

        if let Some(index) = l.iter().find(|&&x| x as isize > prev_pos) {
            prev_pos = *index as isize;
            flg = false;
        }
        else {
            prev_pos = *l.iter().min().unwrap() as isize;
            ans += len_s as isize;
            flg = true;
        }
    }
    if flg == false {
        ans += prev_pos + 1;
    }

    println!("{}", ans);
}

#[allow(dead_code)]
fn read<T: std::str::FromStr>() -> T  {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().parse::<T>().ok().unwrap()
}

#[allow(dead_code)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace()
    .map(|e| e.parse().ok().unwrap())
    .collect()
}