C++ assignment with first == last

#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> first;
  std::vector<int> second;

  first.assign (7,100);             // 7 ints with a value of 100

  std::vector<int>::iterator it;
  it=first.begin()+1;

  second.assign (it,it);
  std::cout << "Size of second: " << int (second.size()) << '\n';
  return 0;
}

Output is:

Size of second: 0