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>

int main() {
  char s[100001], t[100001];
  scanf("%s %s", s, t);
  int ls = strlen(s), lt = strlen(t), substr[ls+1][26]; long ans = 0;
  for (int i=0; i<26; i++) substr[ls][i] = -1;
  for (int i=ls-1; i>=0; i--) {
    for (int j=0; j<26; j++) substr[i][j] = substr[i+1][j];
    substr[i][s[i]-'a'] = i;
  }
  int idx = 0;
  for (int i=0; i<lt; i++) {
    int numt = t[i]-'a';
    if (substr[0][numt] == -1) {
      printf("-1\n");
      return 0;
    }
    if (substr[idx][numt] == -1) {
      ans += ls-idx;
      idx = 0;
    }
    ans += substr[idx][numt]+1 - idx;
    idx = substr[idx][numt]+1;
  }
  printf("%ld\n", ans);
  return 0;
}