#528 Minimum Replacements for a Good String

A string s containing only lowercase Latin letters is given. A string is considered good if both "tbank" and "study" occur in it as substrings.

Find the minimum number of characters that must be changed so that the resulting string becomes good.

Input:

• A string s, where 10 <= |s| <= 10^5;
• The string is guaranteed to contain only lowercase Latin letters.

Output:

• One number — the minimum number of characters that must be replaced so that both "tbank" and "study" occur as substrings.

Examples:

"tbankstudy" -> 0  (already contains both substrings)
"studtbankk" -> 5  (5 characters must be changed)

public static int solve(String s) {
    // TODO
}