C++ car parking management system

This is C++ car parking management system. The statement of car parking management system is:

There are three floors in a building and every floor has capacity of ten cars to park.one floor is for Civic, one for Accord and one for City. Whenever a car system should ask either it is civic, Accord or City and it should be park on its floor if there exists room.

#include<iostream>

using namespace std;

enum{M=10};

class park

{private:

int capacity[M];int front,rear,g;

public:

            park()

            {front=rear=-1;g=0;}

            void inpark()

            {if(rear==M-1)

            {cout<<"floor is full,no room for any car more"<<endl;return;}

            else

            {if(front==-1)

            {rear++;front++;g++;

            capacity[rear]=g+1;

            cout<<"your car has parked "<<endl<<endl;}

            else

            {rear++;g++;

            capacity[rear]=g+1;

            cout<<"your car has parked "<<endl<<endl;}}}

            void outpark()

            {if(front==-1)

            {cout<<"there is no car in this floor "<<endl<<endl;}

            else

            {rear--;

            cout<<"remaining cars on this floor are   "<<rear<<endl<<endl;}}};

            void main()

            {park a,b,c;

            char x;

            start:

            cout<<"if u want to park a CIVIC ,then press 'A'  "<<endl;

            cout<<"if u want to park a CITY,then press 'B'  "<<endl;

            cout<<"if u want to park a Accord,then press 'C'  "<<endl;

            cout<<"if u want to car back,then press 'S'"<<endl;

            cout<<"if u want to exit,then press 'x' "<<endl;

            cin>>x;

            if(x=='A')

            {system("cls");a.inpark();goto start;}

            if(x=='B')

            {system("cls");b.inpark();goto start;}

            if(x=='C')

            {system("cls");c.inpark();goto start;}

            if(x=='S')

            {system("cls");

            cout<<"if u want to car back a CITY car,press 'C'"<<endl;

            cout<<"if u want to car back a CIVIC car,press 'D'"<<endl;

            cout<<"if u want to car back a Accord car,press 'E'"<<endl;

            cout<<"if u want to exit,then press 'x' "<<endl;

            cin>>x;

            if(x=='C')

            {system("cls");b.outpark();goto start;}

            if(x=='D')

            {system("cls");a.outpark();goto start;}

            if(x=='E')

            {system("cls");c.outpark();goto start;}}

            if(x=='x')

            {goto end;}

            else

            {cout<<"u entered wrong choice  "<<endl;

            goto start;}

end:

            system("pause");}