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: Accepted)

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

#define S_MAX 100001
#define T_MAX 100001

int b_search(int arr[], int num, int left, int right){
  if(left == right) return arr[left];
  int mid = (left+right)/2;
  if(arr[mid] > num) return b_search(arr, num, left, mid);
  else return b_search(arr, num, mid+1, right);
}

int main(void){
  int i, j, k;

  char s[S_MAX], t[T_MAX];
  scanf(" %s", s);
  scanf(" %s", t);

  int s_len = strlen(s);

  int alp[26][S_MAX] = {}, alp_num[26] = {}, c_num;
  for(i = 0; i < s_len; i++){
    c_num = s[i]-'a';
    alp[c_num][alp_num[c_num]] = i+1;
    alp_num[c_num]++;
  }

  for(i = 0; i < 26; i++){
    if(alp[i][0] == 0) continue;
    alp[i][alp_num[i]] = alp[i][0]+s_len;
  }

  long ans = 0;
  int prev_pos = 0, next_pos = 0;
  for(i = 0; i < strlen(t); i++){
    c_num = t[i]-'a';
    if(alp[c_num][0] == 0){
      printf("-1\n");
      return 0;
    }
    next_pos = b_search(alp[c_num], prev_pos, 0, alp_num[c_num]);
    ans += next_pos - prev_pos;
    prev_pos = next_pos%s_len;
  }

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

  return 0;
}