std distance c++

// C++ program to demonstrate std::distance() 
#include <iostream> 
#include <vector> 
#include <iterator> 
using namespace std; 
int main() 
{ 
    vector<int> v; 
    int i; 
  
    for (i = 0; i < 10; ++i)  
    { 
        v.push_back(i); 
    } 
  
    /*v contains 0 1 2 3 4 5 6 7 8 9*/
  
    vector<int>::iterator first; 
    vector<int>::iterator last; 
  
    // first pointing to 0 
    first = v.begin(); 
  
    // last pointing to 5 
    last = v.begin() + 5; 
  
    // Calculating no. of elements between first and last 
    int num = std::distance(first, last); 
  
    // Displaying num 
    cout << num << "\n"; 
    return 0; 
}