C++ program :Array of all prime numbers less then or equal to n (SIEVEN)

#include<iostream>
using namespace std;
int main()
{
int A[20],B[20],i,n,j;
cout<<"Enter the positive intiger:";
cin>>n;
for(i=2;i<=n;i++)
B[i]=i;
for(i=2;i<=n;i++)
{
if(B[i]!=0)
{   j=i*i;
   while(j<=n)
  {  B[j]=0;
     j+=i;
   }
}
}

j=0;
for(i=2;i<=n;i++)
{ 
if(B[i])
{
A[j++]=B[i];
cout<<B[i]<<"\t";
}
}
cout<<endl;
return(0);
}