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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <malloc.h>
#include <string.h>

int main(void)
{
    char *s = (char *)calloc(100001, sizeof(char));
    char *t = (char *)calloc(100001, sizeof(char));
    int *ret = (int *)calloc(100001, sizeof(int));
    int *ccount = (int *)calloc(26, sizeof(int));
    int **pos;

    int i, j, k, x;
    int slen, tlen;
    char c;
    long min = 0;
    int count;

    int n;

    scanf("%s", s);
    scanf("%s", t);

    slen = strlen(s);
    tlen = strlen(t);

    // create table
    pos = (int **)calloc(26, sizeof(int *));
    for (i = 0; i < 26; i++)
    {
        pos[i] = (int *)calloc(100000 + 1, sizeof(int));
    }

    // pus table
    for (i = 0; i < slen; i++)
    {
        count = pos[s[i] - 'a'][0];
        pos[s[i] - 'a'][count + 1] = i + 1;
        pos[s[i] - 'a'][0] = count + 1;
    }

    /*
    for (i = 0; i < 26; i++)
    {
        printf("%c : ", 'a' + i);
        for (j = 0; j < pos[i][0]; j++)
        {
            printf("%d ", pos[i][j + 1]);
        }
        printf("\n");
    }
    */

    // Search character position
    for (i = 0; i < tlen; i++)
    {
        c = t[i];

        // exist in s ?
        if (pos[c - 'a'][0] == 0)
        {
            printf("-1\n");
            return 0;
        }

        n = ccount[c - 'a'];
        if (n > pos[c - 'a'][0])
        {
            ret[i] = pos[c - 'a'][1];
            ccount[c - 'a'] = 1;
        }
        else
        {
            ret[i] = pos[c - 'a'][n + 1];
            ccount[c - 'a'] = n + 1;
        }
    }

    /*
    for (i = 0; i < tlen; i++)
    {
        printf("%d\n", ret[i]);
    }
    */

    min = ret[0];

    for (i = 1; i < tlen; i++)
    {
        // in s
        if (ret[i - 1] < ret[i])
        {
            min = min + (ret[i] - ret[i - 1]);
        }
        else
        {
            min = min + (slen - ret[i - 1]) + ret[i];
        }
    }

    printf("%ld\n", min);

    free(s);
    free(t);
    free(pos);

    return 0;
}