jjj

package pu;

import java.util.Scanner;

public class hw1 {

	public static void main(String[] args) {

		Scanner input = new Scanner (System.in);
		int n;
		do {
			System.out.println("Choose an operation");
			System.out.println("1. Fibonacci;");
			System.out.println("2. Perfect numbers;");
			System.out.println("3. Sum;");
			System.out.println("0. Exit");
			n = input.nextInt();
			switch (n) {
			case 1: {
				System.out.println("Please enter a number :)");
				int k = input.nextInt();
				System.out.println("Fibonacci numbers: ");
				int F = 0, i, p=1, f=0;
				for(i=0;i<k;i++) {
				if(i<2) { F=i;}
				else if (i>=2)
				{
					F=f+p;
					f=p;
					p=F;
				}
				System.out.print(F + " ");
				}
				System.out.println();
				}
			 break;


			case 2:{
				System.out.println("Perfect numbers between 1 and 10 000:");
				for(int i=1; i<=10000; i++) {
					int sum=0;
					for(int j=1; j<i;j++)
					{
						if (i%j==0) sum=sum + j;
					}
					if (sum==i)	System.out.print(i + " ");


				}
				System.out.println();

			} break;

			case 3:{
				int S=0;
				System.out.println("Sum of the numbers between 1 and 10 000:");
				for(int i=0;i<=1000;i++ )
				{
					S=S+i;
				}System.out.println(S);
				System.out.println();
			} break;

			case 0:
				System.exit(0);

			default: {
				System.out.println("Please enter a number between 0 and 3!");
				System.out.println();
				}break;

			}
		}

			while (n!=0);

			input.close();
		}

}