Program to find sum of square of n natural numbers

#include<iostream.h>
#include<conio.h>

void main()
{
clrscr();
unsigned long n,i,sum=0,d;
cout<<"\n Enter a number : ";
cin>>n;

for(i=1;i<=n;++i)
{
d=i*i;
sum+=d;
}
cout<<"\n\t Sum = "<<sum;
getch();
}


                                                            Output