How to Call base Class Constructor

[Exceter]

hi
help me with the following plz, I have base class , it has two constructors, in derived class I want to call the base classes different constructors
for ex.,
class X {
public:
X();
X(int);
} ;
class Y : public X {
public:
Y();
f() {//call X()};
G() {//call X(int)};
};

how can I call in 1-function one constructor, and in second function second constructor of the base class?

tnx.