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::*;
use std::str::FromStr;

fn main() {
    let s: Vec<char> = read::<String>().chars().collect();
    let t: Vec<char> = read::<String>().chars().collect();

    let mut data: Vec<Vec<usize>> = vec![vec![]; 26];
    for i in 0..s.len() {
        let c = s[i] as usize;
        data[c - ('a' as usize)].push(i);
    }
    
    let mut ans: usize = 0;
    let mut last = 0;
    let mut check = false;
    for i in 0..t.len() {
        let c = t[i] as usize;
        let po = &data[c - ('a' as usize)];
        if po.len() == 0 {
            check = true;
            break;
        }

        if i == 0 {
            ans += po[0]+1;
            last = po[0];
            continue;
        }

        let mut ok = po.len() as isize;
        let mut ng = -1;
        while ok - ng > 1 {
            let mid = ((ok + ng) / 2) as usize;
            if po[mid] <= last {
                ng = mid as isize;
            } else {
                ok = mid as isize;
            }
        }
        let ok = ok as usize;
        if ok == po.len() {
            ans += s.len() - last + po[0];
            last = po[0];
        } else {
            ans += po[ok] - last;
            last = po[ok];
        }
    }
    if check {
        println!("-1");
    } else {
        println!("{}", ans);
    }
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}