How do I call a member's constructor when declaring a structure?

[The Pondermatic]

I created a structure, and its members are objects that require a constructor with an argument to be called to work. How do I call the objects' constructors when I declare an instance of the structure?

This is the structure:

struct full_set
{
	key n,e,d;//n, e, and d are instances of the key class.
};

This is the key class:

class key
{
public:
	key(int);//key.length is set to the value passed to the constructor.
	//Other member functions
private:
	int *keyset;//keyset is a dynamic array
	bool *defined_keys;//defined_keys is a dynamic array
	int length;//length is the length of the dynamic arrays
};

key::key(int set_length)
{//key.length is set to the value passed to the constructor.
	length = set_length;
	//Also, create the dynamic arrays.
	keyset = new int[length];
	defined_keys = new bool[length];
	//more code
}

Since the constructor in the key class creates the dynamic arrays, it needs to be called whenever an instance is created. When I create an instance of the full_set structure, how do I call the constructor for its members?