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: Accepted)

use std::io::Read;

fn run() {
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let s = it.next().unwrap();
    let t = it.next().unwrap();
    let mut a = vec![vec![]; 26];
    for (i, c) in s.chars().enumerate() {
        let k = (c.to_digit(36).unwrap() - 10) as usize;
        a[k].push(i);
    }
    let n = s.len();
    for k in 0..26 {
        if a[k].is_empty() {
            continue;
        }
        let x = a[k][0];
        a[k].push(x + n);
    }
    let mut pos = 0;
    let mut sum = 0;
    for c in t.chars() {
        let k = (c.to_digit(36).unwrap() - 10) as usize;
        if a[k].is_empty() {
            println!("-1");
            return;
        }
        let x = a[k].binary_search(&pos).unwrap_or_else(|p| p);
        sum += a[k][x] - pos + 1;
        pos = (a[k][x] + 1) % n;
    }
    println!("{}", sum);
}

fn main() {
    run();
}