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: Wrong Answer)

#include<bits/stdc++.h>

#define int long long
using namespace std;
#define rep(i, n) for(int i=0;i<(n);++i)
typedef pair<int, int> pii;
const int INF = 1l << 60;
#define u_b upper_bound
#define l_b lower_bound

string S, T;
int pos[26][100100];

signed main() {
    cin >> S >> T;
    set<char> ss;
    for (char s:S) {
        ss.insert(s);
    }
    for (char t:T) {
        if (ss.count(t) == 0) {
            cout << -1 << endl;
            return 0;
        }
    }

    rep(i, 26)rep(j, 100100)pos[i][j] = -1;

    rep(i, S.size()) {
        int c = S[i] - 'a';
        int k = i;
        while (pos[c][k] == -1) {
            pos[c][k] = i;
            --k;
            if (k == -1)k = S.size() - 1;
        }
    }
    int num = 0;
    int prev = 0;
    rep(i, T.size()) {
        int cur = pos[T[i] - 'a'][prev + 1];
        if (cur <= prev)num++;
        prev = cur;
    }
    cout << num * S.length() + prev + 1 << endl;
    return 0;
}