Problem programmer?

in main:

vector<int> player_nr;
int x = menu(player_nr.begin());

menu function:

int menu(vector<int>::iterator x)
{
...
int a = x->size(); //<---- complains here
...
}

As far as I understood it Vectors have the arrow-operator defined in C++. Then why the fuck does the compilator complain of it?

>>5

Which is why I use the arrow-operator (->) to use the "size()" function on the vector instead of on the iterator. Did I missunderstand how this works?