/in/foo.cc: In function 'int main()':
/in/foo.cc:20:4: error: 'cin' was not declared in this scope
    cin>>a;
    ^~~
/in/foo.cc:20:4: note: suggested alternative:
In file included from /in/foo.cc:2:0:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:21:24: error: 'strlen' was not declared in this scope
  for(int i=0;i<strlen(a);i++){
                        ^
/in/foo.cc:25:17: error: 'max' was not declared in this scope
   mx=max(mx,a[i]);
                 ^
/in/foo.cc:25:17: note: suggested alternative:
In file included from /usr/include/c++/6/bits/char_traits.h:39:0,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:2:
/usr/include/c++/6/bits/stl_algobase.h:265:5: note:   'std::max'
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/in/foo.cc:26:17: error: 'min' was not declared in this scope
   mn=min(mn,a[i]);
                 ^
/in/foo.cc:26:17: note: suggested alternative:
In file included from /usr/include/c++/6/bits/char_traits.h:39:0,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:2:
/usr/include/c++/6/bits/stl_algobase.h:243:5: note:   'std::min'
     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/in/foo.cc:29:3: error: 'cout' was not declared in this scope
   cout<<"Lucky Word\n"<<mx-mn;
   ^~~~
/in/foo.cc:29:3: note: suggested alternative:
In file included from /in/foo.cc:2:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~