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: Wrong Answer)

#[test]
fn test_solve() {
   assert_eq!(solve("contest\nson\n"), "10\n");
   assert_eq!(solve("contest\nprogramming\n"), "-1\n");
   assert_eq!(solve("contest\nsentence\n"), "33\n");
}
fn solve(src: &str) -> String {
    let mut sc = Scanner::from_str(src);

    let s: Vec<_> = sc.get().chars().collect();
    let t: Vec<_> = sc.get().chars().collect();

    const code_a: usize = 'a' as usize;
    let cod = |c: char| c as usize - code_a;

    let mut nxt = vec![Vec::new(); cod('z')+1];
    for i in 0..s.len() {
        nxt[cod(s[i])].push(i)
    }
    let mut nxt: Vec<_> = nxt.iter().map(|vec| vec.iter().cycle()).collect();

    let mut lp = 0;
    let mut idx = 0;
    for &c in &t {
        if let Some(&i) = nxt[cod(c)].next() {
            if i < idx {
                lp += 1; 
            }
            idx = i;
        } else {
            return "-1\n".to_string()
        }
    }   

    format!("{}\n", lp * s.len() + idx + 1)
}
fn main() {
    let mut buf = String::new();
    use std::io::{Read, Write};
    std::io::stdin().read_to_string(&mut buf).unwrap();
    std::io::stdout().write_all(solve(&buf).as_bytes()).unwrap();
}
struct Scanner<'a>(std::str::SplitWhitespace<'a>);
impl<'a> Scanner<'a> {
    fn from_str(src: &str) -> Scanner {
        Scanner(src.split_whitespace())
    }
    fn get(&mut self) -> &str {
        self.0.next().unwrap()
    }
    fn read<T: std::str::FromStr>(&mut self) -> T {
        self.get().parse().ok().unwrap()
    }
}