Why won't sort() or unique() work with an int vector (C++)?

sort() and unique() won't work with such a simple int vector. Any suggestions are welcome.

std::vector<int>vec {33,25,11,44,22,20,12,33,59,87,23,53,26,44,26,97,22,32,44,43,44};
std::sort(vec.begin(), vec.end());
std::unique(vec.begin(), vec.end());

int nr = 1;
std::cout << std::endl;
for (auto p = vec.begin(); p!=vec.end(); p++){
    std::cout << *p << " ";
    if (!(nr++%4)) std::cout << std::endl;
}

returns:

11 12 20 22
23 25 26 32
33 43 44 53
59 87 97 44
44 53 59 87
97 21

Note that the numbers are neither sorted, not duplicates are expelled (I marked 44, 53).

**UPD: thanks to the contributors, here's the solution: instead of

std::unique(vec.begin(), vec.end());

we type:

    auto last = std::unique(vec.begin(), vec.end());//returns an iterator to non-unique elements
    vec.erase(last, vec.end());// and kills them