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)

pub 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()
}

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

pub fn read_vec2<T: std::str::FromStr>(n: usize) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

pub fn read_col<T: std::str::FromStr>(n: usize) -> Vec<T> {
    (0..n).map(|_| read()).collect()
}

fn f(u: usize, p: usize, c: u64, edges: &Vec<Vec<(usize, u64)>>, depth: &mut Vec<u64>) {
    depth[u as usize] = c;
    for v in &edges[u] {
        if v.0 == p {
            continue;
        }
        f(v.0, u, c + v.1, edges, depth);
    }
}

fn dist(a: u32, b: u32) -> u32 {
    if a > b {
        a - b
    } else {
        b - a
    }
}

fn atou(a: char) -> usize {
    (a as usize) - 97
}

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

    let svec: Vec<char> = s.chars().collect();
    let tvec: Vec<char> = t.chars().collect();

    let mut next: Vec<Vec<usize>> = vec![vec![1000000; 26]; s.len()];
    let mut tmp: Vec<usize> = vec![1000000; 26];
    for i in (0..s.len()).rev() {
        next[i] = tmp.clone();
        tmp[atou(svec[i])] = i;
    }
    for i in (0..s.len()).rev() {
        next[i] = tmp.clone();
        tmp[atou(svec[i])] = i;
    }

    let mut id: usize = 1000000;
    for i in 0..s.len() {
        if svec[i] == tvec[0] {
            id = i;
            break;
        }
    }
    if id > 100000 {
        println!("-1");
        return;
    }
    let mut dis = id + 1;
    let mut ans: u64 = dis as u64;
    for i in 1..t.len() {
        let nextid = next[id][atou(tvec[i])];
        if nextid > 100000 {
            println!("-1");
            return;
        }
        dis = (nextid + s.len() - id) % s.len();
        if dis == 0 {
            dis = s.len();
        }
        id = nextid;
        ans += dis as u64;
    }

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