/in/foo.cc: In function 'int main()':
/in/foo.cc:62:68: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    while (!qp->empty() && tp < k && f[tp][l[x]] >= 0 && qn->size() < k)
                                                         ~~~~~~~~~~~^~~
/in/foo.cc:75:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    while (!qp->empty() && qn->size() < k)
                           ~~~~~~~~~~~^~~
/in/foo.cc:77:52: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    while (tp < k && f[tp][l[x]] >= 0 && qn->size() < k)
                                         ~~~~~~~~~~~^~~