Program to find twin prime numbers.

Program to find twin prime numbers. Please comment if you need help.

#include<stdio.h>
void main( )
{
int  i,n,k,r,a[50],p;
printf("nEnter the range:  ");
scanf("%d", &r);
i=1;
p=0;
while(i<=r)
{
k=0;
n=1;
while(n<=i)
{
if( i%n==0 )
k++;
n++;
}
if(k==2)
{
a[p]=i;
p++;
}
i++;
}
for(n=0;n<p;n++)
{
if(a[n+1] - a[n]==2)
printf("\n%d and %d are twin primes", a[n], a[n+1]);
}
}