Erase member function of vector class

[ivanov ivan ivanovich]

In the following code, the iterator points to the next element of deleted element of vector.
Can you please explain it to me.
Thank you.

#include <iostream>
#include <vector>
using namespace std;

int main()
{
  int arr[]={2,5,7,9};
  vector<int> v(arr,arr+sizeof(arr)/sizeof(int));
  vector<int>::iterator it;
  int i(1);
  while (it!=v.end()){
    it=v.begin();
    cout<<"round "<<i<<":"<<endl;
    cout<<"The first vector element before erasing: "<<*it<<endl;
    v.erase(it);
    cout<<"The value that iterator contains after erasing: "<<*it<<endl;
    cout<<"The first vector element after erasing: "<<v.front()<<endl;
    i++;
  }
  
}

OUTPUT:
round 1:
The first vector element before erasing: 2
The value that iterator contains after erasing: 5
The first vector element after erasing: 5
round 2:
The first vector element before erasing: 5
The value that iterator contains after erasing: 7
The first vector element after erasing: 7
round 3:
The first vector element before erasing: 7
The value that iterator contains after erasing: 9
The first vector element after erasing: 9
round 4:
The first vector element before erasing: 9
The value that iterator contains after erasing: 9
The first vector element after erasing: 9

[JLBorges]

std::vector::erase
Invalidates iterators and references at or after the point of the erase, including the end() iterator.

Return value: Iterator following the last removed element. If the iterator pos refers to the last element, the end() iterator is returned.
http://en.cppreference.com/w/cpp/container/vector/erase

#include <iostream>
#include <vector>

int main() {

    std::vector<int> v { 2, 5, 7, 9 };

    std::vector<int>::iterator it = v.begin() ;

    while( it != v.end() ) {

        std::cout << "erase " << *it << '\n' ;
        it = v.erase(it) ; // returns the iterator to the element just after the
                           // removed element, or end() if there is no such element
    }
}