Write the constructor inside the class.
Person(int a, int b, int c)
{
x=a;
y=b;
z=c;
}
And change
Person p = new Person(x, y, z);
to
Person p(x, y, z); //if you just want to make an object p
or to
Person* p = new Person(x, y, z); //if you want a pointer p to point to a Person object
//your code goes here
//But in this case, you will have to explicitly deallocate the space you've allocated for p
delete p;