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)

#[allow(unused_macros)]
macro_rules! input {
    ($x:expr) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        $x = buf.trim().parse().unwrap();
    };

    ($x:expr, $($y:expr), +) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).ok();
        input_iter!(buf.split_whitespace(), $x, $($y), +);
    };

    ($v:expr; $size:expr) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).ok();
        for v in buf.split_whitespace() {
            $v.push(v.parse().unwrap());
        }
    };

    ($v:expr; $h_size:expr, $w_size:expr) => {
        for _ in 0..$h_size {
            let mut part_vec = Vec::new();
            let mut buf = String::new();
            std::io::stdin().read_line(&mut buf).ok();
            for v in buf.split_whitespace() {
                part_vec.push(v.parse().unwrap());
            }
            $v.push(part_vec);
        }
    };
}

#[allow(unused_macros)]
macro_rules! input_iter {
    ($iter:expr, $x:expr) => {
        $x = $iter.next().unwrap().parse().unwrap();
    };

    ($iter:expr, $x:expr, $($y:expr), +) => {
        let mut iter = $iter;
        $x = iter.next().unwrap().parse().unwrap();
        input_iter!(iter, $($y), *);
    };
}

#[allow(unused_imports)]
use std::collections::*;
use std::collections::hash_map::Entry::*;

fn main() {
    let s: String;
    let t: String;
    input! { s };
    input! { t };
    let mut hm: HashMap<char, Vec<usize>> = HashMap::new();
    for (i, c) in s.chars().enumerate() {
        hm.entry(c).or_insert(Vec::new()).push(i);
    }
    let mut set_num = 0;
    let mut cur_idx = 0;
    for c in t.chars() {
        if let Vacant(_) = hm.entry(c) {
            print!("-1");
            return;
        }
        let v = hm.get(&c).unwrap();
        let mut idx = match v.binary_search(&cur_idx) {
            Ok(x) => x,
            Err(x) => x,
        };
        if idx >= v.len() {
            set_num += 1;
            idx = 0;
        }
        cur_idx = v[idx] + 1;
    }
    println!("{}", set_num * s.len() + cur_idx);
}