WRONG

#include<iostream>
#include<iomanip>
#include<cmath>
#include<math.h>

#define PI 3.14

using namespace std;

void aos(){
	double side,aosquare;
	cout << "Input side: " << endl;
	cin >> side;
		if (side < 0){
			cout <<"ERROR! Please input a positive number!" << endl;
			aos();
		}
	aosquare = pow(side,2);
	cout << "Area of square is " << aosquare << "." << endl;
}

void por(){
	double l, w;
	cout << "Input length and width" << endl;
	cin >> l >> w;
		if (l < 0 && w < 0){
			cout <<"ERROR! Please input a positive number!" << endl;
			por();
		}
	double prectangle;
	prectangle = l * w;
	cout << "Perimeter of Rectangle: " << prectangle << endl;
}

void voc(){
	cout <<"Input r and h: " << endl;
	double r, h, vcylinder;
	cin >> r >> h;
		if(r < 0 && h < 0)
		{
			cout <<"ERROR! Please input a positive number!" << endl;
			voc();
		}
	vcylinder = (PI) * pow(r,2) * h;
	cout << "The volume of the cylinder is " << vcylinder << endl;
}

int main(){
	cout << "Developed by: Francis Gabriento" << endl;
	cout << "Station No.: 34" << endl;
	cout <<"MENU" << endl;
	double = choice;
	cout << "\t [1] Area of Square " << endl;
	cout <<"\t [2] Perimeter of a Rectangle" << endl;
	cout << "\t[3] Volume of a Cylinder " << endl;
	cout <<"Key in your choice: ";
	cin >> choice;
		switch(choice){
			case "1":
				aos();
				break;
			case "2":
				por();
				break;
			case "3":
				voc();
				break;
			default:
				cout << "You chose an Unknown Number!" << endl;
				cout <<"Please choose between [1], [2], and [3]" << endl << endl << endl;
				main();
				break;
		}
}