finding area using function overloading

#include<iostream>
using namespace std;
#include<conio.h>
#define pi 3.142

void area(int);
void area(float);
void area(float, float);

void main()
{
int ch,s;
float l,b,r;
do
{
cout<<"-----MENU----- \n";
cout<<"1. Square \n";
cout<<"2. Circle \n";
cout<<"3. Rectangle \n";
cout<<"4. Exit \n\n";

cout<<"Make a choice: ";
cin>>ch;
switch(ch)
{
case 1:
cout<<"Enter side of Square: ";
cin>>s;
area(s);
break;
case 2:
cout<<"Enter radius of Circle: ";
cin>>r;
area(r);
break;
case 3:
cout<<"Enter length of Rectangle: ";
cin>>l;
cout<<"Enter breadth of Rectangle: ";
cin>>b;
area(l,b);
break;
case 4:
exit(0);
default:
cout<<"Invalid Choice \n";
break;
}
}
while(ch!=4);
getch();
}
void area(int s)
{
int area;
area=s*s;
cout<<"The Area of Square= "<<area<<"\n";
}
void area(float r)
{
float area;
area=pi*r*r;
cout<<"The Area of Circle= "<<area<<"\n";
}
void area(float l, float b)
{
float area;
area=l*b;
cout<<"The Area of Rectangle= "<<area<<"\n";
}