/*tim hai so nguyen to co tong bang 1 so chan cho truoc*/

#include<stdio.h>

#include<conio.h>

int nto(int k)

{

    int nt=0;

    for(int i=2;i<k;i++)

       if(k%i==0)

           nt=1;//bien nt dung de xac dinh da thuc hien phep chia

    if(nt==0)  return 1;//ko chia het cho so nao thi thuc hien tiep ham

    else      return 0;

}//ham xac dinh so nto

int main()

{

    int n,i,j,t,a[50];

    do

    {

    printf("nhap vao so chan%d",&n);

    }while((n%2)!=0);//xac dinh so n nhap vao phai la so chan

    t=0;

    for(i=2;i<n;i++)

    {

       if(nto(i))

          a[t]=i;

          t++;

    }//xac dinh co bao nhieu so nto trong khoang 2->n

    printf("hai so nguyen to  co tong bang %d la: ",n);

    for(i=0;i<t;i++)//chay tu 0->t

      for(j=i;j<t;j++)//chay tu i->t,xac dinh dc so i roi moi den j

      if((a[i]+a[j]==n)&&(a[i]!=a[j]))//neu so nto a+so nto b=n, a#b

         printf("

%d,%d",a[i],a[j]);//thi in ra a,b

    getch();

    return 0;

}

//VD:n=12-> co 4 so nto trong khoang 0-12

//=>t=3

//i:0-3,a[0]=3,a[1]=5,a[2]=7,a[3]=11