Find error in my code (C++)

//RECTANGLE
#include<iostream.h>
#include<conio.h>
#include<math.h>
#include<process.h>
main()
{
clrscr();
int ch;
char ch1;
long float l,b,area,peri,diag;
cout<<"Rectangle Menu: \n";
cout<<"1.Area\n";
cout<<"2.Perimeter\n";
cout<<"3.Diagonal\n";
cout<<"4.Exit\n";
cout<<"Enter your choice(1-4): ";
do
	{
	cin>>ch;
	if(ch==1 || ch==2 || ch==3)
	{	cout<<"Enter Length and Breadth :\n";
		cin>>l>>b;
	}
	switch(ch)
	{
	case'1':
		area=l*b;
		cout<<"Area= "<<area;
		break;
	case'2':
		peri=2*(l+b);
		cout<<"Perimeter= "<<peri;
		break;
	case'3':
		diag=sqrt((l*l)+(b*b));
		cout<<"Diagonal= "<<diag;
		break;
	case'4':
		cout<<"Exiting....";
		exit(0);
	default:
		cout<<"Wrong choice!!!!";
		cout<<"Enter a valid choice";
		break;
	}
	cout<<"\nWant to enter more(y/n)? ";cin>>ch1;
	if(ch1=='y' || ch1=='Y')
		cout<<"Again enter choice(1-4): ";
	}
	while(ch1=='y' || ch1=='Y');
getch();
}