/* 驗(yàn)證歌德巴赫猜想----Author:zhg_2006.04.25
*/
#include<stdio.h>
#include<math.h>
int isprime(int z);
void zhg_information(char Date[]);
extern char Date[]={"2006.4.25"};
void main()
{
  int i,n,x,y,k;
  zhg_information(Date);
  printf("\n\t\t\t\t\t\t\t      For exit,input 0.\n\n\n\n\t");
  printf("\n\n\n  Please enter an even number n(%%d>=6):   ");
  biaohao: scanf("%d",&n);
  if(n==0)
    goto over;
  if(n<6||n%2!=0)
  {
    zhg_information(Date);
    printf("\n\t\t\t\t\t\t\t      For exit,input 0.\n\n\n\n");
    printf("\tERROR INPUT !\n\n\n  Please Enter another number. OK ?   ");
    goto biaohao;
  }
  zhg_information(Date);
  printf("\n\t\t\t\t\t\t\t      For exit,input 0.\n\n");
  printf("  Last result:\n");
  for(k=1,i=3;i<=n/2;i++)
  {
    x=isprime(i);
    if(x==1)
    {
      y=isprime(n-i);
      if(y==1)
      {
	printf("  (%d): %d=%d+%d    ",k,n,i,n-i);
	if(k%3==0)
	  putchar('\n');
	k++;
     //	break;                 /*With this there will show only one result.*/
      }
    }
  }
  printf("\n\n\n\n\tContinue:   ");
  goto biaohao;
  over:;
}
int isprime(int z)
{
  int k,w;
  if(z==3)
  w=1;
  for(k=2;k<=sqrt(z);k++)
  {
    if(z%k==0)
    {
      w=0;
      break;
    }
    if(k==(int)sqrt(z))
    w=1;
  }
  return w;
}


#include<stdio.h>
#include<conio.h>
void zhg_information(char Date[])       
{
  int i;
  clrscr();
  printf("\n\t\t\t   All  Rights  Reserved !!!\n");
  printf(" Wuhan University\t\t\t\t\t\t----Author: zhg\n");
  printf(" E-mail: wudazhg@163.com%55s\n",Date);
  for(i=1;i<=80;i++)
    putchar('-');
  putchar('\n');
}