Language: C++

  /*****************************************************************\
    |     IN THE NAME OF ALLAH, MOST GRACIOUS AND MOST MERCIFUL       |
    |                                                                 |
    |     Author     : Mahabub Rahman                                 |
    |     Email      : mahabubrahman618@gmail.com                     |
    |     University : Comilla University, Bangladesh		          |
    |                  Department of Computer Science & Engineering   |
    \*****************************************************************/
 
 
    /*...................................Data_Types............................................*/
    #include<bits/stdc++.h>
 
    using namespace std;
    #define FastIO ios::sync_with_stdio(false); cin.tie(0);cout.tie(0)
    #define       ll                  long long int
    #define       ull                  unsigned long long int
    #define       veci                 vector<int>
    #define       vecc                 vector<char>
    #define       vecs                 vector<string>
    #define       vecl                 vector<long long int>
    #define       vecp                 vector<  pair<int,int> >
    #define       mapstrint            map< string , int >
    #define       mapstrstr            map< string , string >
    #define       mapint               map< int, int >
    #define       pb                   push_back
    #define       pob                  pop_back
    #define       mp                   make_pair
    ////============ CONSTANT ===============////
    #define mx9   1000000007
    #define mx7   10000007
    #define mx6   1000006
    #define mx5   200005
    #define inf   1<<30                                           //infinity value
    #define eps   1e-9
 
    #define mod   1000000007
    ////=====================================////
 
    long double PI = acosl(-1);
    bool compare_int(int a, int b) //This function is use for descending order.
    {
        return (a>b);
    }
    bool compare_string (string a, string b)
    {
        return a.size() < b.size();
    }
    bool compare_pair(const pair<int,int> &a,
                  const pair<int,int> &b)
    {
        if(a.second==b.second) return a.first>b.first;
        else return (a.second > b.second);
    }
    /*ll fact(ll n)
    {
        if(n==0 || n==1) return 1;
        else return n*fact(n-1);
    }*/
 
    ////======================================////
    /*bool check(int n)
    {
        for(int i=2; i<=sqrt(n); i++)
        {
            if(n%i==0)
            {
                return false;
            }
        }
        return true;
    }*/
    int32_t main()
    {
        FastIO;
        //Don't see test case until get 7/8 times wrong submission..!!
        //Try to make Corner, Even, Odd or Prime case..!!
        ll n;
        string s;
        vector<int> r, g, b;
        cin >> n >> s;
        ll cnt = 0;
        for (int i = 0; i<n;i++)
        {
            if(s[i]=='R') r.push_back(i+1);
            else if(s[i]=='G') g.push_back(i+1);
            else b.push_back(i+1);
        }
      int a=r.size(),b=g.size(),c=b.size();
      
        for(int i=0; i<a; i++)
            for(int j=0; j<b; j++)
                for(int k=0; k<c); k++)
                {
                    if(b[k]-g[j]==g[j]-r[i]) continue;
                    if(r[i]-b[k]==b[k]-g[j]) continue;
                    if(g[j]-r[i]==r[i]-b[k]) continue;
                    cnt++;
                }
        cout << cnt << endl;
        return 0;
    }

Compiler output:
a.cc: In function 'int32_t main()':
a.cc:89:22: error: conflicting declaration 'int b'
   89 |       int a=r.size(),b=g.size(),c=b.size();
      |                      ^
a.cc:80:27: note: previous declaration as 'std::vector<int> b'
   80 |         vector<int> r, g, b;
      |                           ^
a.cc:92:27: error: no match for 'operator<' (operand types are 'int' and 'std::vector<int>')
   92 |             for(int j=0; j<b; j++)
      |                          ~^~
      |                          | |
      |                          | std::vector<int>
      |                          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:12:
/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:92:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
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:92:28: note:   mismatched types 'const std::pair<_T1, _T2>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
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:92:28: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
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:92:28: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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:92:28: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   92 |             for(int j=0; j<b; j++)
      |                            ^
/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 __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3874 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note:   template argument deduction/substitution failed:
a.cc:92:28: note:   mismatched types 'const std::__cxx11: