/in/foo.cc: In function 'int dijkstra(int, int, int)':
/in/foo.cc:35:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<edges[c].size();i++){
               ~^~~~~~~~~~~~~~~~
In file included from /usr/include/c++/6/ext/pb_ds/detail/binomial_heap_base_/binomial_heap_base_.hpp:199:0,
                 from /usr/include/c++/6/ext/pb_ds/detail/binomial_heap_/binomial_heap_.hpp:50,
                 from /usr/include/c++/6/ext/pb_ds/detail/priority_queue_base_dispatch.hpp:54,
                 from /usr/include/c++/6/ext/pb_ds/priority_queue.hpp:46,
                 from /in/foo.cc:2:
/usr/include/c++/6/ext/pb_ds/detail/binomial_heap_base_/insert_fn_imps.hpp: In instantiation of '__gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::node_pointer __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::fix(__gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::node_pointer) const [with Value_Type = std::pair<int, int>; Cmp_Fn = cmp; _Alloc = std::allocator<char>; __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::node_pointer = __gnu_pbds::detail::left_child_next_sibling_heap_node_<std::pair<int, int>, long unsigned int, std::allocator<char> >*]':
/usr/include/c++/6/ext/pb_ds/detail/binomial_heap_base_/insert_fn_imps.hpp:100:28:   required from 'void __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::insert_node(__gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::node_pointer) [with Value_Type = std::pair<int, int>; Cmp_Fn = cmp; _Alloc = std::allocator<char>; __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::node_pointer = __gnu_pbds::detail::left_child_next_sibling_heap_node_<std::pair<int, int>, long unsigned int, std::allocator<char> >*]'
/usr/include/c++/6/ext/pb_ds/detail/binomial_heap_base_/insert_fn_imps.hpp:48:14:   required from '__gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::point_iterator __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::push(__gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::const_reference) [with Value_Type = std::pair<int, int>; Cmp_Fn = cmp; _Alloc = std::allocator<char>; __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::point_iterator = __gnu_pbds::detail::left_child_next_sibling_heap_node_point_const_iterator_<__gnu_pbds::detail::left_child_next_sibling_heap_node_<std::pair<int, int>, long unsigned int, std::allocator<char> >, std::allocator<char> >; __gnu_pbds::detail::binomial_heap_base<Value_Type, Cmp_Fn, _Alloc>::const_reference = const std::pair<int, int>&]'
/in/foo.cc:29:17:   required from here
/usr/include/c++/6/ext/pb_ds/detail/binomial_heap_base_/insert_fn_imps.hpp:112:29: error: passing 'const __gnu_pbds::detail::binomial_heap_base<std::pair<int, int>, cmp, std::allocator<char> >' as 'this' argument discards qualifiers [-fpermissive]
       if (Cmp_Fn::operator()(p_nd->m_value, p_next->m_value))
           ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:18:7: note:   in call to 'bool cmp::operator()(const pii&, const pii&)'
  bool operator()(const pii&a, const pii&b){
       ^~~~~~~~