int sub(unsigned long int n)
{
int k=0;
unsigned long int i,j;
for(i=n+1;i<=4294967295;i++)
{
for(j=1;j<=i;j++)
{
if(i%j==0)
k++;
}
if(k==2) break;
k=0;
}
k=0;
int b=i;
for(i=n;i>=1;i--)
{
for(j=1;j<=i;j++)
{
if(i%j==0)
k++;
}
if(k==2) break;
k=0;
}
int a=i;
cout<<a<<" "<<b;
return 0;
}