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 <algorithm>
#include <vector>
#include <string>
using namespace std;
typedef long long ll;

int main()
{
    string s, t;
    cin >> s >> t;
    int n = s.size();
    int m = t.size();
    vector<int> v[26];
    int cals[26] {0};
    int calt[26] {0};
    for(int i = 0; i < n; i++){
        cals[s[i] - 'a']++;
        v[s[i] - 'a'].push_back(i);
    }
    for(int i = 0; i < m; i++){
        calt[t[i] - 'a']++;
    }
    for(int i = 0; i < 26; i++){
        if(cals[i] == 0 && calt[i] != 0){
            cout << -1 << endl;
            return 0;
        }
    }
    for(int i = 0; i < 26; i++){
//        cout << i << " ";
//        for(int x : v[i]) cout << x << " ";
//        cout << endl;
//        cout << cals[i] << endl;
    }
    ll now = -1;
    ll cir = 0;
    for(int i = 0; i < m; i++){
        int u = t[i] - 'a';
//        cout << now << " ";
        int next = upper_bound(v[u].begin(), v[u].end(), now) - v[u].begin();
//        cout << u << " " << next << endl;
        if(next == cals[u]){
//            cout << u << endl;
            now = -1;
            cir++;
            next = upper_bound(v[u].begin(), v[u].end(), now) - v[u].begin();
        }
        now = v[u][next];
//        cout << next << endl;
    }
    ll ans = cir * n + now + 1;
    cout << ans << endl;
//    cout << cir << n << now << endl;
}