Recursive Variable Substitution with Cycle Detection

Given a key-value map kv and a template string template, variable references use the form %KEY%, where KEY contains only uppercase letters, digits, and underscores. Expand every variable reference in the template: Replace %KEY% with kv[KEY]. Values in kv may themselves contain variable references and must be expanded recursively until no expandable references remain. If a referenced key does not exist, print ERROR. If the dependency graph contains a cycle, print CYCLE. Every % is guaranteed to belong to a valid %KEY% placeholder. You do not need to handle escaped percent signs or unmatched % characters. Example: kv = { USER = admin, HOME = /%USER%/home } template = I am %USER%. My home is %HOME%. Output: I am admin. My home is /admin/home. Input Format n KEY_1=VALUE_1 KEY_2=VALUE_2 ... KEY_n=VALUE_n template The first line contains the number of entries n. Each of the next n lines contains one mapping. The text before the first = is the key; everything after it is the value. Values may contain spaces and %KEY% references. The last line is the template to expand. Output Format Print the fully expanded template on success. Print ERROR if an undefined variable is referenced. Print CYCLE if there is a cyclic dependency. Constraints 1 <= n <= 10^5 The total number of characters across all keys, values, and the template is at most 10^6. Each key appears at most once. Example Input 2 USER=admin HOME=/%USER%/home I am %USER%. My home is %HOME%. Output I am admin. My home is /admin/home.