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 {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, bytes) => {
        read_value!($next, String).into_bytes()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}
mod vig {
    pub trait S {
        fn binary_search(&self, key: usize) -> usize;
    }
    impl S for Vec<usize> {
        fn binary_search(&self, key: usize) -> usize {
            let mut ng: i64 = -1;
            let mut ok: i64 = self.len() as i64;
            loop {
                // println!("in {}", ok);
                if (ok - ng).abs() <= 1 {
                    break;
                }
                let mid = (ok + ng) / 2;
                if self[mid as usize] > key {
                    ok = mid;
                } else {
                    ng = mid;
                }
            }
            ok as usize
        }
    }
}
fn main() {
    input!{
        s: chars,
        t: chars
    }
    let mut alp:Vec<Vec<usize>> = vec![vec![];26];
    let mut target:Vec<Vec<usize>> = vec![vec![]; 26];
    for i in 0..s.len() {
        alp[(s[i] as i32 - 97) as usize].push(i);
    }
    for i in 0..t.len() {
        target[(t[i] as i32 - 97) as usize].push(i);
    }
    // println!("{:?}", alp);
    // println!("{:?}", target);
    let mut no = false;
    // let mut ans:i64 = 0;
    for i in 0..26 {
        if alp[i].len()==0 && target[i].len()!=0 {
            no = true;
        }
    }
    let mut v = vec![];
    if no==false{
        let mut prev = 1<<50;
        for i in 0..t.len() {
            // t[i] -> num push & c++ -> BAD!!!!
            // v.push(s) find s by using binary_search
            let ind = (t[i] as i32 - 97) as usize;
            let bin = vig::S::binary_search(&alp[ind], prev);
            let now = if bin == alp[ind].len() {
                0
            }else{
                bin
            };
            // println!("alp {:?}", alp[ind]);
            // println!("now {}", now);
            v.push(alp[ind][now]);
            prev = alp[ind][now];
        }
        // println!("{:?}", v);
        let mut ch = v[0];
        let mut g = 0;
        for i in 1..v.len() {
            if v[i]<=ch {
                g += 1;
            }
            ch = v[i];
        }
        // println!("{}", g);
        let ans = s.len() * g + v[(v.len() as i64 - 1) as usize] + 1;
        println!("{}", ans);
    }else{
        println!("-1");
    }
    // if no {
    // }else{
    // }
}