Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define FOR(i,l,r) for(i=l;i<r;i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define P pair<ll,ll>
#define F first
#define S second
signed main(){
  ll H,W,i,j;P S,G,c=0;cin>>H>>W>>S.F>>S.S>>G.F>>G.S;bool X[H][W];ll Y[H][W];deque<P>B;
  REP(i,H)REP(j,W){char s;cin>>s;X[i][j]=(s=='.');Y[i][j]=H*W;}S.F--;S.S--;G.F--;G.S--;
  B.push_back(S);Y[S.F][S.S]=0;vector<P>O(4);
  O.at(0)=P(-1,0);O.at(1)=P(0,-1);O.at(2)=P(1,0);O.at(3)=P(0,1);
  while(B.size()&&c<500000000){
    P E=B.front();B.pop_front();c++;
    REP(i,4){
      ll x=E.F+O.at(i).F,y=E.S+O.at(i).S;
      if(0<=x&&x<H&&0<=y&&y<W&&X[x][y]&&Y[x][y]>Y[E.F][E.S]){
        Y[x][y]=Y[E.F][E.S];B.push_back(P(x,y));
      }
    }
    FOR(i,-2,3)FOR(j,-2,3)if(abs(i)+abs(j)>1){
      ll x=E.F+i,y=E.S+j;
      if(0<=x&&x<H&&0<=y&&y<W&&X[x][y]&&Y[x][y]>Y[E.F][E.S]+1){
        Y[x][y]=Y[E.F][E.S]+1;B.push_back(P(x,y));
      }
    }
  }
  if(Y[G.F][G.S]==H*W)Y[G.F][G.S]=-1;
  cout<<Y[G.F][G.S]<<endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:22: error: conversion from 'int' to non-scalar type 'std::pair<long long int, long long int>' requested
   11 |   ll H,W,i,j;P S,G,c=0;cin>>H>>W>>S.F>>S.S>>G.F>>G.S;bool X[H][W];ll Y[H][W];deque<P>B;
      |                      ^
a.cc:15:20: error: no match for 'operator<' (operand types are 'std::pair<long long int, long long int>' and 'int')
   15 |   while(B.size()&&c<500000000){
      |                   ~^~~~~~~~~~
      |                   | |
      |                   | int
      |                   std::pair<long long int, long long int>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   mismatched types 'const std::pair<_T1, _T2>' and 'int'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::move_iterator<_IteratorL>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'const std::move_iterator<_IteratorL>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:680:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   'std::pair<long long int, long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/string_view:688:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  688 |     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:688:5: note:   template argument deduction/substitution failed:
a.cc:15:21: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   15 |   while(B.size()&&c<500000000){
      |                     ^~~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx