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 <cstdio>
#include <iostream>
#include <cassert>
#include <string>
#include <algorithm>
#include <cstring>
#include <utility>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cmath>
#include <deque>
#include <unordered_map>
using namespace std;
typedef long long LL;
typedef pair<int, int> pii;
typedef pair<LL, LL> pll;
const int MAXN = 123456;
char s[MAXN], t[MAXN];
vector<int> idx[87];

int main() {
    scanf("%s", s + 1);
    scanf("%s", t + 1);
    int ns = strlen(s + 1);
    int nt = strlen(t + 1);
    for (int i = 1; i <= ns; i++) {
        int cur = s[i] - 'a';
        idx[cur].push_back(i);
    }
    int ans = 0, cur_idx = 0;
    for (int i = 1; i <= nt; i++) {
        int cur = t[i] - 'a';
        if (idx[cur].empty()) return !printf("-1\n");
        int tmp = upper_bound(idx[cur].begin(), idx[cur].end(), cur_idx) - idx[cur].begin();
        //printf("i = %d tmp = %d\n", i, tmp);
        if (tmp == (int)idx[cur].size()) {
           ans += (ns - cur_idx);
           cur_idx = idx[cur].front();
           ans += cur_idx;
        } else {
           ans += (idx[cur][tmp] - cur_idx);
           cur_idx = idx[cur][tmp];
        }
    }
    printf("%d\n", ans);
    return 0;
}