Language: C++

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

int main() {
	int n; cin >> n;
	vector<string>s(n);
	for (int i = 0; i < n; i++) cin >> s[i];

	string abc = "abcdefghijklmnopqrstuvwxyz";
	string ans;
	for (int i = 0; i < 26; i++) {
		int cnt = (int)1e9;
		for (int j = 0; j < s.size(); j++) {
			cnt = min(cnt, count(s[j].begin(), s[j].end(), abc[i]));
		}
		for (int j = 0; j < cnt; j++) {
			ans += abc[i];
		}
	}
	cout << ans << endl;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:17:34: error: no matching function for call to 'min(int&, std::__iterator_traits<__gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >, void>::difference_type)'
   17 |                         cnt = min(cnt, count(s[j].begin(), s[j].end(), abc[i]));
      |                               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:17:34: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::__iterator_traits<__gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >, void>::difference_type' {aka 'long int'})
   17 |                         cnt = min(cnt, count(s[j].begin(), s[j].end(), abc[i]));
      |                               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:17:34: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   17 |                         cnt = min(cnt, count(s[j].begin(), s[j].end(), abc[i]));
      |                               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~