#include <iostream>
#include <vector>
#include <cassert>

int main() {
    std::vector<int> v { 1, 2, 3, 4 };
    auto it = cbegin(v);
    assert(it != cend(v));
    std::cout << (*it) << std::endl;
    ++it;
    assert(it != cend(v));
    std::cout << (*it) << std::endl;
    it++;
    assert(it != cend(v));
    std::cout << (*it) << std::endl;
    it = std::next(it);
    assert(it != cend(v));
    std::cout << (*it) << std::endl;
}