/in/foo.cc: In function 'int main()':
/in/foo.cc:81:26: warning: variable 'nb' set but not used [-Wunused-but-set-variable]
             pair<int,int>nb = rel(e->first);
                          ^~
/in/foo.cc:77:23: warning: variable 'sup' set but not used [-Wunused-but-set-variable]
         pair<int,int> sup= rel(e->first);
                       ^~~