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 (1.42.0) (judge verdict: Accepted)

#[allow(unused_imports)]
use proconio::input;
#[allow(unused_imports)]
use proconio::marker::Chars;
#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused)]
const ALPHA_SMALL: [char; 26] = [
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
    't', 'u', 'v', 'w', 'x', 'y', 'z',
];
#[allow(unused)]
const ALPHA: [char; 26] = [
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
    'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
];
#[allow(unused)]
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}
#[allow(unused)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}
#[allow(unused)]
fn read_touple<T: std::str::FromStr + Copy>() -> (T, T) {
    let v: Vec<T> = read_vec();
    assert_eq!(v.len(), 2);
    (v[0], v[1])
}

use std::collections::HashMap;

fn main() {
    input!(s: Chars);
    input!(t: Chars);
    let n = s.len();
    let m = t.len();
    let mut hash: HashMap<char, Vec<usize>> = HashMap::new();
    for (i, &c) in s.iter().enumerate() {
        let v = hash.entry(c).or_insert_with(|| vec![]);
        v.push(i);
    }
    for (i, &c) in s.iter().enumerate() {
        let v = hash.entry(c).or_insert_with(|| vec![]);
        v.push(n + i);
    }

    //println!("{:?}", hash);
    let mut ans = 0;
    let mut p = 0;
    for &c in &t {
        if let Some(v) = hash.get(&c) {
            p = match v.binary_search(&p) {
                Ok(j) => v[j] + 1,
                Err(j) => v[j] + 1,
            };
            //println!("{}", p);
            if p >= n {
                p -= n;
                ans += n;
            }
        } else {
            println!("{}", -1);
            return;
        }
    }
    ans += p;
    println!("{}", ans);
}