to compile:
$ make
to run:
$ ./main

default contructor:
VecInt a; // empty vector

constructor with size and initial value:
VecInt a(2); // a = {0 , 0}
VecInt a(3, 9); // a = {9, 9, 9}

initializer list constructor:
VecInt a = {1, 2, 3};

copy/move contructor:
VecInt a = {1, 2, 3};
VecInt b(a); 

= // assignment operator
[] // subscript operator
== // equal operator
!= // not equal operator

size()
begin()
end()

sort()
reverse()