Language: C++

#include<iostream>
#include<algorithm>
#include<map>
#include<vector>
using namespace std;

map<int,int> a;
vector<int> b;

int n,m;
char z;
int main(){
	while(cin>>n>>z>>m){
		if(a.find(n)==a.end())a.insert(n,1);
		else a[n]++;
	}
	while(cin>>n>>z>>m){
		if(a.find(n)!=a.end())b.push_back(n);
	}
	sort(b.begin(),b.end());
	for(int i=0;i<b.size();i++)cout<<n<<" "<<a[n]<<endl;
	return 0;
}

Compiler output:
In file included from /usr/include/c++/14/map:63,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_map.h: In instantiation of 'void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = int; _Tp = int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]':
a.cc:14:33:   required from here
   14 |                 if(a.find(n)==a.end())a.insert(n,1);
      |                                       ~~~~~~~~^~~~~
/usr/include/c++/14/bits/stl_map.h:943:38: error: no matching function for call to 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::_M_insert_range_unique(int&, int&)'
  943 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/map:62:
/usr/include/c++/14/bits/stl_tree.h:1096:9: note: candidate: 'template<class _InputIterator> std::__enable_if_t<((bool)std::is_same<_Val, typename std::iterator_traits<_InputIterator>::value_type>::value)> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_range_unique(_InputIterator, _InputIterator) [with _Key = int; _Val = std::pair<const int, int>; _KeyOfValue = std::_Select1st<std::pair<const int, int> >; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]'
 1096 |         _M_insert_range_unique(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1096:9: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_tree.h: In substitution of 'template<class _InputIterator> std::__enable_if_t<((bool)std::is_same<std::pair<const int, int>, typename std::iterator_traits< <template-parameter-1-1> >::value_type>::value), void> std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::_M_insert_range_unique(_InputIterator, _InputIterator) [with _InputIterator = int]':
/usr/include/c++/14/bits/stl_map.h:943:31:   required from 'void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = int; _Tp = int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]'
  943 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
a.cc:14:33:   required from here
   14 |                 if(a.find(n)==a.end())a.insert(n,1);
      |                                       ~~~~~~~~^~~~~
/usr/include/c++/14/bits/stl_tree.h:1095:58: error: no type named 'value_type' in 'struct std::iterator_traits<int>'
 1095 |         __enable_if_t<__same_value_type<_InputIterator>::value>
      |                                                          ^~~~~
/usr/include/c++/14/bits/stl_map.h: In instantiation of 'void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = int; _Tp = int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]':
a.cc:14:33:   required from here
   14 |                 if(a.find(n)==a.end())a.insert(n,1);
      |                                       ~~~~~~~~^~~~~
/usr/include/c++/14/bits/stl_tree.h:1105:9: note: candidate: 'template<class _InputIterator> std::__enable_if_t<((bool)(! std::is_same<_Val, typename std::iterator_traits<_InputIterator>::value_type>::value))> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_range_unique(_InputIterator, _InputIterator) [with _Key = int; _Val = std::pair<const int, int>; _KeyOfValue = std::_Select1st<std::pair<const int, int> >; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]'
 1105 |         _M_insert_range_unique(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1105:9: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_tree.h: In substitution of 'template<class _InputIterator> std::__enable_if_t<((bool)(! std::is_same<std::pair<const int, int>, typename std::iterator_traits< <template-parameter-1-1> >::value_type>::value)), void> std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::_M_insert_range_unique(_InputIterator, _InputIterator) [with _InputIterator = int]':
/usr/include/c++/14/bits/stl_map.h:943:31:   required from 'void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = int; _Tp = int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int> >]'
  943 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
a.cc:14:33:   required from here
   14 |                 if(a.find(n)==a.end())a.insert(n,1);
      |                                       ~~~~~~~~^~~~~
/usr/include/c++/14/bits/stl_tree.h:1104:59: error: no type named 'value_type' in 'struct std::iterator_traits<int>'
 1104 |         __enable_if_t<!__same_value_type<_InputIterator>::value>
      |                                                           ^~~~~