CF1295C Obtain The String

You are given two strings $ s $ and $ t $ consisting of lowercase Latin letters. Also you have a string $ z $ which is initially empty. You want string $ z $ to be equal to string $ t $ . You can perform the following operation to achieve this: append any subsequence of $ s $ at the end of string $ z $ . A subsequence is a sequence that can be derived from the given sequence by deleting zero or more elements without changing the order of the remaining elements. For example, if $ z = ac $ , $ s = abcde $ , you may turn $ z $ into following strings in one operation: 1. $ z = acace $ (if we choose subsequence $ ace $ ); 2. $ z = acbcd $ (if we choose subsequence $ bcd $ ); 3. $ z = acbce $ (if we choose subsequence $ bce $ ). Note that after this operation string $ s $ doesn't change. Calculate the minimum number of such operations to turn string $ z $ into string $ t $ .

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