Calculate Website User Conversion Rate from Events

uber In a concurrent system, calculate the conversion rate of users from visiting a website to completing a purchase. Suppose there are a series of event records, each record containing a user ID, an event type (including 'visit' and 'purchase'), and a timestamp. Please write a program to calculate the overall conversion rate. Input The first line is an integer $N$, representing the number of events. The next $N$ lines, each line contains a user ID (string), an event type (string: 'visit' or 'purchase'), and a timestamp (integer). Output Print a float number representing the conversion rate, rounded to two decimal places. Example Input: 5 A visit 1 B visit 2 A purchase 3 B purchase 4 C visit 5 Output: 1.00 Constraints $1 \leq N \leq 10^5$ Each user has at most one visit and one purchase event. Timestamps are strictly increasing. Example Input 5 A visit 1 B visit 2 A purchase 3 B purchase 4 C visit 5