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: Wrong Answer)

#if 0
date +%Y.%m.%d

题解先咕着。
#endif
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
#define debug(...) fprintf(stderr, __VA_ARGS__)

typedef long long lolong;

inline int input() { int x; scanf("%d", &x); return x; }

const int maxn = 100005;
char s[maxn], t[maxn];
std::vector<int> pos[26];

int main() {
	scanf("%s", s);
	scanf("%s", t);
	int n = int(strlen(s));
	int m = int(strlen(t));

	for(int i = 0; i < n; i ++)
		pos[s[i] - 'a'].push_back(i);

	int a = 0, b = 0;
	for(int i = 0; i < m; i ++) {
		auto it = std::lower_bound(pos[t[i] - 'a'].begin(), pos[t[i] - 'a'].end(), b);
		if(it == pos[t[i] - 'a'].end()) {
			a ++;
			b = 0;
			it = std::lower_bound(pos[t[i] - 'a'].begin(), pos[t[i] - 'a'].end(), b);
			if(it == pos[t[i] - 'a'].end()) {
				puts("-1");
				return 0;
			}
		}
		b = *it + 1;
		if(b == n + 1) {
			a ++;
			b = 0;
		}
	}

	printf("%d\n", a * n + b);
}