[백준_JAVA_알고리즘] 2839 설탕 배달

import java.util.Scanner;
 
public class Main {
	public static void main(String[] args) {
    
		Scanner scanner = new Scanner(System.in);
        
		int N = scanner.nextInt();
		
		if (N == 4 || N == 7) {
			System.out.println(-1);
		}
		else if (N % 5 == 0) {
			System.out.println(N / 5);
		}
		else if (N % 5 == 1 || N % 5 == 3) {
			System.out.println((N / 5) + 1);
		}
		else if (N % 5 == 2 || N % 5 == 4) {
			System.out.println((N / 5) + 2);
		}
		scanner.close();
	}
}