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: Time Limit Exceeded)

use std::io::stdin;
use std::time::SystemTime;
use std::collections::HashMap;

#[allow(dead_code)]
fn read_line() -> String {
    let mut s = String::new();
    stdin().read_line(&mut s).unwrap();
    s.trim().to_string()
}

#[allow(dead_code)]
fn read<T>() -> T
where T: std::str::FromStr
{
    read_line().parse::<T>().ok().unwrap()
}

#[allow(dead_code)]
fn read_vec<T>() -> Vec<T>
where T: std::str::FromStr
{
    read_line().split(" ").map(|n| n.parse::<T>().ok().unwrap()).collect()
}

#[allow(dead_code)]
fn read_chars() -> Vec<char>
{
    read_line().chars().collect()
}

#[allow(dead_code)]
fn print_time() -> () {
    println!("{:?}", SystemTime::now());
}

trait BinarySearchLeft<T> {
    fn binary_search_left(&self, x: &T) -> Result<usize, usize>;
}

impl<T> BinarySearchLeft<T> for Vec<T>
where T: std::cmp::Ord + std::fmt::Debug
{
    fn binary_search_left(&self, x: &T) -> Result<usize, usize> {
        let index = self.binary_search(x);
        match index {
            Ok(index) => {
                for i in (1..index+1).rev() {
                    if self[i] != self[i - 1] {
                        return Ok(i - 1)
                    }
                }
                
                Ok(index)
            },
            _ => index,
        }
    }
}

#[allow(unused_variables)]
fn main() {
    let s = read_chars();
    let t = read_chars();

    for p in t.iter() {
        if !s.contains(p) {
            println!("-1");
            return
        }
    }

    let mut h = HashMap::<char, Vec<usize>>::new();
    for i in 0..s.len() {
        let c = s[i];
        if h.get(&c).is_some() {
            let v = h.get_mut(&c).unwrap();
            v.push(i);
        } else {
            h.insert(c, vec![i]);
        }
    }

    let mut bl = 0;
    let mut before = h.get(&t[0]).unwrap()[0];
    for i in 1..t.len() {
        let c = t[i];

        let mut f = true;
        while f {
            let p = h.get(&c).unwrap();
            let a = (bl * s.len()) + p[p.len() - 1];
            if before < a {
                for j in 0..p.len() {
                    let b = (bl * s.len()) + p[j];
                    if before < b {
                        before = b;
                        f = false;
                        break;
                    }
                }
            }

            if f {
                bl += 1;
            }
        }
    }

    println!("{}", before + 1);
}