/in/foo.cc: In function 'void merge(long long int, long long int)':
/in/foo.cc:15:23: error: no matching function for call to 'find()'
     p[find(x)] = find();
                       ^
/in/foo.cc:10:5: note: candidate: long long int find(long long int)
 int find(int x){
     ^~~~
/in/foo.cc:10:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/c++/6/algorithm:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:65,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_algo.h:3784:5: note: candidate: template<class _IIter, class _Tp> _IIter std::find(_IIter, _IIter, const _Tp&)
     find(_InputIterator __first, _InputIterator __last,
     ^~~~
/usr/include/c++/6/bits/stl_algo.h:3784:5: note:   template argument deduction/substitution failed:
/in/foo.cc:15:23: note:   candidate expects 3 arguments, 0 provided
     p[find(x)] = find();
                       ^
In file included from /usr/include/c++/6/bits/locale_facets.h:48:0,
                 from /usr/include/c++/6/bits/basic_ios.h:37,
                 from /usr/include/c++/6/ios:44,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/streambuf_iterator.h:369:5: note: candidate: template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(std::istreambuf_iterator<_CharT>, std::istreambuf_iterator<_CharT>, const _CharT2&)
     find(istreambuf_iterator<_CharT> __first,
     ^~~~
/usr/include/c++/6/bits/streambuf_iterator.h:369:5: note:   template argument deduction/substitution failed:
/in/foo.cc:15:23: note:   candidate expects 3 arguments, 0 provided
     p[find(x)] = find();
                       ^
/in/foo.cc: At global scope:
/in/foo.cc:17:10: error: '::main' must return 'int'
 int main(){
          ^