How can I make constructor?

#include
#include
#include
#define pi 3.14
using namespace std;

class won{

private:
	float answer;
	float radius;
	float nop;
public:
	won(float radius){
	this -> radius = radius;
	}
	won(float radius, float nop){
		this -> radius = radius;
		this -> nop = nop;
	}
	
	float nul(float radius){//넓이 구하는 함수
		answer = pow(radius,2)*pi;
		return answer;	
	}
	
	float gu(float radius){//구의 넓이 구하는함수
		float circle = pow(radius,3); // r의 세제곱
		answer = pi*circle*4/3;
		return answer; 
	}
	
	float gidung(float nop){//원기둥 함수
		answer = nul(radius)*nop;
		return answer;
	}
	
	float bbul(){//원뿔 함수
		int dap = gidung(radius);
		answer = dap/3;
		return answer;
	}

};

int main(){
float answer;
int radius = 0;

while(1){
cout << "반지름 입력 : ";
cin >> radius;
int nop;
int select;

system("cls");
cout << "메뉴" << endl << endl;
cout <<"1. 원의 넓이 2. 구의 부피 3. 원기둥의 부피 4.원뿔의 부피" << endl;

cin >> select;

switch(select){

		case 1://원의 넓이
		won a(radius);
		answer = a.nul(radius);
		cout << "원의 넓이는 " << answer << "입니다";
	case 2://구의 부피
		won b(radius);
		answer = b.gu();
		cout << "구의 부피는 " << answer << "입니다";
	case 3://원기둥의 부피
		cin >> nop;
		won c(radius, nop);
		answer = c.gidung();
		cout << "원기둥의 부피는 " << answer << "입니다";
	case 4:;//원뿔의 부피
		cin >> nop;
		won d(radius, nop);
		answer = won.bbul();
		cout << "원뿔의 부피는 " << answer << "입니다";
}

}
return 0;
}

It is not works please help me

You’ll have to tell us a) what the goal is; b) how it “not works” before anyone can help.

Assuming this is C++, I see one issue: the lack of a “break;” statement at the end of each “case” block.