import java.util.Scanner;
import java.util.Queue;
import java.util.LinkedList;

public class BankQueueSimulation {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入顾客总人数N: ");
        int N = scanner.nextInt();

        Queue<Customer> customerQueue = new LinkedList<>();
        System.out.println("请输入每位顾客的到达时间T和处理时间P，按到达时间先后顺序输入:");
        for (int i = 0; i < N+1; i++) {
            int arrivalTime = scanner.nextInt();
            int processTime = scanner.nextInt();
            customerQueue.add(new Customer(arrivalTime, processTime));
        }

        System.out.print("请输入每位顾客事务被处理的最长时间MaxProc（分钟）: ");
        int MaxProc = scanner.nextInt();
        System.out.print("请输入银行最多可开设的营业窗口MaxWindow: ");
        int MaxWindow = scanner.nextInt();

        double averageWaitTime = simulateQueue(customerQueue, MaxProc, MaxWindow);
        System.out.printf("所有顾客的平均等待时间为: %.2f 分钟%n", averageWaitTime);
    }

    private static double simulateQueue(Queue<Customer> customerQueue, int MaxProc, int MaxWindow) {
        int totalWaitTime = 0;
        int numCustomers = customerQueue.size();
        int[] windowEndTime = new int[MaxWindow];

        while (!customerQueue.isEmpty()) {
            Customer currentCustomer = customerQueue.poll();
            int minEndTime = Integer.MAX_VALUE;
            int chosenWindow = -1;

            // 找到最早可用的窗口
            for (int i = 0; i < MaxWindow; i++) {
                if (windowEndTime[i] < minEndTime) {
                    minEndTime = windowEndTime[i];
                    chosenWindow = i;
                }
            }

            int waitTime = Math.max(0, minEndTime - currentCustomer.arrivalTime);
            totalWaitTime += waitTime;

            // 更新该窗口的结束时间
            windowEndTime[chosenWindow] = currentCustomer.arrivalTime + waitTime + Math.min(currentCustomer.processTime, MaxProc);
        }

        return (double) totalWaitTime / numCustomers;
    }

    static class Customer {
        int arrivalTime;
        int processTime;

        public Customer(int arrivalTime, int processTime) {
            this.arrivalTime = arrivalTime;
            this.processTime = processTime;
        }
    }
}