import java.util.Scanner;

public class DataUsageCostCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Read input
        double dataUsed = scanner.nextDouble();

        // Check for invalid input
        if (dataUsed <= 0) {
            System.out.println("Invalid Input");
        } else if (dataUsed <= 2) {
            // No extra cost for up to 2 GB
            System.out.println(0);
        } else {
            // Calculate extra data and cost
            double extraData = dataUsed - 2;
            int cost = (int) Math.ceil(extraData * 20); // ₹20 per GB
            System.out.println(cost);
        }

        scanner.close();
    }
}