C/C++ Program to calculate area of circle

//Program to calculate area of circle
#include<iostream>
using namespace std;
int main()
{
    double n,r,d,area;
    cout<<"\n You want to calculate area of circle using";
    cout<<"\n 1.Radius \n 2.Diameter"<<endl;
    cout<<"\n Enter your choice:";
    cin>>n;
    if(n==1)
          {
        cout<<"\n Enter radius:";
        cin>>r;       
        cout<<"\n Area of circle ="<<3.14*2*r<<endl;
          }
       
    else if(n==2)
          {
        cout<<"\n Enter diameter:";
        cin>>d;       
        cout<<"\n Area of circle ="<<3.14*d<<endl;
          }
    else
        cout<<"\n Invalid choice"<<endl;
return 0;
}