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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main(void) {
    string s, t;
    cin >> s >> t;
    s.insert(0, " ");

    vector<int[26]> next(s.size());

    int tmp[26];
    for(int i=0; i<26; i++) {
        tmp[i] = -1;
    }

    for(int i=s.size()-1; i>=0; i--) {
        for(int j=0; j<26; j++) {
            if(tmp[j] < 0) {
                next[i][j] = tmp[j];
            } else {
                next[i][j] = tmp[j] - i;
            }
        }
        tmp[s[i]-'a'] = i;
    }

    int64_t now = 0;
    int64_t ans = 0;
    for(int i=0; i<t.size(); i++) {
        int64_t jump = next[now][t[i]-'a'];
        if(now == 0 && jump == -1) {
            cout << -1 << endl;
            return 0;
        } else if(jump >= 0) {
            now += jump;
            ans += jump;
        } else {
            ans += s.size()-1-now;
            now = 0;
            --i;
        }
    }

    cout << ans << endl;
    return 0;
}