A puzzle for me (cookie)

Today, i met a problem.. I'm a new man in C++ programer.

So it's reserved for me... I believe I would get it.

#include <iostream>
using nameapce std;

int main(){
string str;
auto sp = str.begin(); /// str.begin()??
while (cin >> str) {
cout << *sp << endl;
}
}

if we input "abc", the console return the 'a'.. the next time, we input the "jame", the console return the 'a'.. why ?

Let's made some changes in this program!

#include <iostream>
using namespace std;

int main(){
string str;
while(cin >> str) {
auto sp = str.begin(); /// place it in the different place.
cout << *sp << endl;
}
}

what you got? the first element in str. why?

Let's make more changes.

#include <iostream>
using namespace std;

int main(){
string str, *sp;
sp = &str;
while ( cin >> str){
// remove the str.begin(), replaced with string pointer.
cout << (*sp)[0] << endl;
}
}

what do we get? the same behavior as the second one.