#include <iostream>
#include <iterator>
#include <vector>
using namespace std;
int main() 
{
    vector<int> v;
    v.push_back(3);
    v.push_back(1);
    v.push_back(4);
    cout << "distance(first, last) = "
              << distance(v.begin(), v.end()) <<endl
              << "distance(last, first) = "
              << distance(v.end(), v.begin()) <<endl;
}

distance(first, last) = 3
distance(last, first) = -3