//twin prime 
#include<math.h>
#include<stdio.h>
#include<conio.h>
int prime(int);
void main()
{
clrscr();
int n,k,i,flag=0;
printf("\n Enter the range lower limit and upper limit:");
scanf("%d %d",&n,&k);
for(i=n;i<=k;i++)
{
if(prime(i)==1 && prime(i+2)==1)
	{
	printf("\n (%d,%d)  is a pair of twin prime:",i,i+2);
	flag=1;
	}
}
if(flag==0)
printf("\n no twin prime in the given range:");
getche();
}
int prime(int n)
{
int i,rem,k=0;
for(i=2;i<=sqrt(n);i++)
	{
	rem=n%i;
	if(rem==0)
		{
		k++;
		}
	}
if(k>0)
return 0;
else
return 1;
}