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 <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <limits.h>
#define Max(a, b) ((a) > (b) ? (a) : (b))
#define Min(a, b) ((a) > (b) ? (b) : (a))
#define abs(x) ((x) > 0 ? (x) : -(x))
#define MOD 1000000007 //10^9 + 7
#define endl printf("\n")
typedef long long ll;
#define MAX_N (1 << 17)

int nal[100002][26];

int
main(int argc, char *argv[])
{
  char s[100001], t[100001];
  scanf("%s", s);
  scanf("%s", t);

  int al[30] = {};
  int ns = strlen(s), nt = strlen(t);
  for (int i = 0; i < ns; i++) al[s[i] - 'a']++;
  for (int i = 0; i < nt; i++) {
    if (al[t[i] - 'a'] == 0) {
      printf("-1\n");
      return 0;
    }
  }

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

  nal[ns][s[ns - 1]] = ns;
  for (int i = ns - 1; i >= 1; i--) {
    for (int j = 0; j < 26; j++) nal[i][j] = nal[i + 1][j];
    nal[i][s[i - 1] - 'a'] = i;
  }

  ll k = 0;
  while(s[k] != t[0]) k++;
  k += 1;

  int e = 1; int tmp;
  while(e < nt){
    tmp = k % (ll)ns;
    if(nal[tmp + 1][t[e] - 'a'] != -1) {
      k += (ll)(nal[tmp + 1][t[e] - 'a'] - tmp);
      e++;
    }
    else {
      k += (ll)ns - k % (ll)ns;
    }
  }

  printf("%lld\n", k);

  return 0;
}