Language: C++

#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

int main() {
	string s;cin>>s;
	bool s=false,ca=false,sm=false;
	for(char c:s){
		if('0'<=c&&c<='9')s=true;
		if('a'<=c&&c<='z')sm=true;
		if('A'<=c&&c<='Z')ca=true;
	}
	if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
	else puts("VALID");
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:14: error: conflicting declaration 'bool s'
    7 |         bool s=false,ca=false,sm=false;
      |              ^
a.cc:6:16: note: previous declaration as 'std::string s'
    6 |         string s;cin>>s;
      |                ^
a.cc:13:13: error: no match for 'operator&&' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'bool')
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |            ~^~~~
      |            |  |
      |            |  bool
      |            std::string {aka std::__cxx11::basic_string<char>}
a.cc:13:13: note: candidate: 'operator&&(bool, bool)' (built-in)
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |            ~^~~~
a.cc:13:13: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'bool'
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166,
                 from a.cc:1:
/usr/include/c++/14/bits/valarray_after.h:415:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__logical_and, typename _Dom1::value_type>::result_type> std::operator&&(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  415 |     _DEFINE_EXPR_BINARY_OPERATOR(&&, struct std::__logical_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:415:5: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/bits/valarray_after.h:415:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__logical_and, typename _Dom1::value_type>::result_type> std::operator&&(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  415 |     _DEFINE_EXPR_BINARY_OPERATOR(&&, struct std::__logical_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:415:5: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/bits/valarray_after.h:415:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__logical_and, typename _Dom1::value_type>::result_type> std::operator&&(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  415 |     _DEFINE_EXPR_BINARY_OPERATOR(&&, struct std::__logical_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:415:5: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'bool'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/bits/valarray_after.h:415:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__logical_and, typename _Dom1::value_type>::result_type> std::operator&&(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  415 |     _DEFINE_EXPR_BINARY_OPERATOR(&&, struct std::__logical_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:415:5: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/bits/valarray_after.h:415:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__logical_and, typename _Dom1::value_type>::result_type> std::operator&&(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  415 |     _DEFINE_EXPR_BINARY_OPERATOR(&&, struct std::__logical_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:415:5: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'bool'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/valarray:1206:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__logical_and, _Tp>::result_type> std::operator&&(const valarray<_Tp>&, const valarray<_Tp>&)'
 1206 | _DEFINE_BINARY_OPERATOR(&&, __logical_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1206:1: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/valarray:1206:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__logical_and, _Tp>::result_type> std::operator&&(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1206 | _DEFINE_BINARY_OPERATOR(&&, __logical_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1206:1: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~
/usr/include/c++/14/valarray:1206:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__logical_and, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__logical_and, _Tp>::result_type> std::operator&&(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1206 | _DEFINE_BINARY_OPERATOR(&&, __logical_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1206:1: note:   template argument deduction/substitution failed:
a.cc:13:15: note:   mismatched types 'const std::valarray<_Tp>' and 'bool'
   13 |         if(s&&sm&&ca&&s.size()>=6)puts("INVALID");
      |               ^~