Output of C++ code

Question

Can someone explain why this code outputs 6? It is completely mind-boggling to me...

#include <iostream>
#include <vector>
using namespace std;
class A{
public:
static int cnt;
A(int a){}
~A(){++cnt;}
};
int A::cnt = 0;

int main() {
vector<A> v(4,1);
v.push_back(1);
cout << A::cnt << endl;
return 0;
}

Answer 1

Here is an exact match to your question where it is already explained:

https://www.sololearn.com/discuss/2028288/?ref=app

And here are very similar problems that deal with the same underlying mechanics:

https://www.sololearn.com/discuss/1501191/?ref=app
https://www.sololearn.com/discuss/1019036/?ref=app
https://www.sololearn.com/discuss/1510164/?ref=app
https://www.sololearn.com/discuss/1203725/?ref=app

Answer 2

Shadow thank you very much!