Calculate Visited Countries

Problem Overview

• Given a bidirectional flight network of n countries forming a tree, each marked Open or Restricted.
• For each country as a start, find the maximum countries visitable when Restricted can be converted to Open only in pairs, not exceeding the number of Restricted; sum these maxima across all starts.
• Input: n (<=50005), edges, and status of each country; Output: the total sum.
• Real-world Covid flight rules context with permission constraints.
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