Language: C++

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

int main(){

  string s;
  cin>>s;
  
  int a=stoi(s[0]);
  int b=stoi(s[1]);	
  int c=stoi(s[2]);
  int d=stoi(s[3]);
  
  if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
  if(a+b+c-d==7)cout<<a<<"+"<<b<<"+"<<c<<"-"<<d<<"==7"<endl;
  if(a+b-c+d==7)cout<<a<<"+"<<b<<"-"<<c<<"+"<<d<<"==7"<endl;
  if(a+b-c-d==7)cout<<a<<"+"<<b<<"-"<<c<<"-"<<d<<"==7"<endl;
  if(a-b+c+d==7)cout<<a<<"-"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
  if(a-b+c-d==7)cout<<a<<"-"<<b<<"+"<<c<<"-"<<d<<"==7"<endl;
  if(a-b-c+d==7)cout<<a<<"-"<<b<<"-"<<c<<"+"<<d<<"==7"<endl;
  if(a-b-c-d==7)cout<<a<<"-"<<b<<"-"<<c<<"-"<<d<<"==7"<endl;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:13: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   12 |   int a=stoi(s[0]);
      |         ~~~~^~~~~~
In file included 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,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:13:13: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   13 |   int b=stoi(s[1]);
      |         ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:14:13: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   14 |   int c=stoi(s[2]);
      |         ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:15:13: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   15 |   int d=stoi(s[3]);
      |         ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:17:55: error: no match for 'operator<' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181:
/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:17:56: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   'std::basic_ostream<char>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   couldn't deduce template parameter '_Bi_iter'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   couldn't deduce template parameter '_Bi_iter'
   17 |   if(a+b+c+d==7)cout<<a<<"+"<<b<<"+"<<c<<"+"<<d<<"==7"<endl;
      |                                                        ^~~~
/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:17:56: note:   'std::basic_ostream<char>' is not derived from 'const s