package kiemtra;

import java.io.*;

import java.net.*;

public class mang {

  public static int nhap(){

    String st;

    int n;

    //do{

        DataInputStream stream =new DataInputStream(System.in);

    try{

       st=stream.readLine();

    }catch(IOException e) {st="0";}

    try{

      n=Integer.valueOf(st).intValue();

    }catch(NumberFormatException e) {n=0;}

    return n;

    //}while (n<0);

  }

  public static float tbc(int a,int b){

    float tbc=(float)a/b;

    return tbc;

  }

    public static void main(String[] args) {

     int[]a=new int[50];

       int n,i,j,k,tongchan=0,ptc=0;

       float TBC=0;

       System.out.println("nhap vao so phan tu cho mang:");

       do{

           n=nhap();

       }while(n<0);

       System.out.println("nhap cac phan tu mang:");

       for (i=0;i<n;i++){

           System.out.print("a["+i+"]=");

           a[i]=nhap();

       }

       System.out.print("mang vua nhap la a["+n+"]:");

       for(i=0;i<n;i++){

          // System.out.println("a[="+i+"]=" +a[i]);

           System.out.print(" "+a[i]);

       }

       for (i=0;i<n;i++){

           if (i%2==0){

           tongchan=tongchan+a[i];

           ptc=ptc+1;

       }

        }

       TBC=tbc(tongchan,ptc);

       System.out.println();

       System.out.println("tong cac phan tu chan trong mang:"+tongchan);

       System.out.println("trung binh cong cac phan tu chan trong mang bang: "+(float)TBC);

   }

}