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: Accepted)

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#define MOD 1000000007
#define mkp make_pair
typedef long long ll;
using namespace std;

string S;
string T;

int nxt[100010][26];

void chmin(int &a,int b){
  if(a>b) a=b;
}

int main(){
  cin>>S;
  cin>>T;
  int N=S.size();
  int M=T.size();

  for(int i=0;i<=N;i++) for(int j=0;j<26;j++) nxt[i][j]=N;
  for(int i=N-1;i>=0;i--){
    for(int j=0;j<26;j++){
      chmin(nxt[i][j],nxt[i+1][j]);
    }
    nxt[i][S[i]-'a']=i;
  }

  for(int i=0;i<M;i++){
    if(nxt[0][T[i]-'a']==N){
      cout<<-1<<endl;
      return 0;
    }
  }

  ll ans=0;
  ll v=0;
  int now=0;
  for(int i=0;i<M;i++){
    if(nxt[now][T[i]-'a']<N){
      now=nxt[now][T[i]-'a']+1;
      if(i==M-1){
        v=now;
        break;
      }
      if(now==N){
        ans++;
        now=0;
      }
    }else{
      now=0;
      ans++;
      i--;
    }
  }

  cout<<ans*N+v<<endl;

  return 0;
}