Как сделать что бы программа не завершалась

#include <iostream>
using namespace std;
int main()
{
int a =0;
cout << "Enter number: ";
cin >> a;
int b =a*a;
cout << a << " in squared = " << b << endl;
system("pause");
return 0;
}

 
#include <iostream>
using namespace std;
int main()
{
do
{
int a =0;
cout << "Enter number: ";
cin >> a;
int b =a*a;
cout << number << " in squared = " << b << endl;
} while (true);
system("pause");
return 0;
}

cout << a << " in squared = " << b << endl;

#include <iostream>
#include <windows.h>
using namespace std;
 
int main()
{
    while (true)
    {
        int a =0;
        cout << "Enter number: ";
        cin >> a;
        int b =a*a;
        cout << a << " in squared = " << b << endl;
    }
 
    return 0;
}

{
do
}

#include <iostream>
using namespace std;
 
int main()
{
    cout << "(Enter -1 for exit)\n";
    int n;
    do {
        n = 0;
        cout << "Enter number: ";
        cin >> n;
        if(n!=-1)
            cout << n << " in squared is " << n*n << "\n";
    } while(n!=-1);
 
    return 0;
}