/in/foo.cc: In function 'int main()':
/in/foo.cc:22:24: error: 'strlen' was not declared in this scope
  for(int i=0;i<strlen(a);i++){
                        ^
/in/foo.cc:26:17: error: no matching function for call to 'max(int&, char&)'
   mx=max(mx,a[i]);
                 ^
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:219:5: note: candidate: template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:219:5: note:   template argument deduction/substitution failed:
/in/foo.cc:26:17: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'char')
   mx=max(mx,a[i]);
                 ^
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: candidate: template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:265:5: note:   template argument deduction/substitution failed:
/in/foo.cc:26:17: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'char')
   mx=max(mx,a[i]);
                 ^
/in/foo.cc:27:17: error: no matching function for call to 'min(int&, char&)'
   mn=min(mn,a[i]);
                 ^
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:195:5: note: candidate: template<class _Tp> const _Tp& std::min(const _Tp&, const _Tp&)
     min(const _Tp& __a, const _Tp& __b)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:195:5: note:   template argument deduction/substitution failed:
/in/foo.cc:27:17: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'char')
   mn=min(mn,a[i]);
                 ^
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: candidate: template<class _Tp, class _Compare> const _Tp& std::min(const _Tp&, const _Tp&, _Compare)
     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^~~
/usr/include/c++/6/bits/stl_algobase.h:243:5: note:   template argument deduction/substitution failed:
/in/foo.cc:27:17: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'char')
   mn=min(mn,a[i]);
                 ^