Language: C++

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
#include<tuple>
#include<unordered_set>
#include<random>
#include<array>
#include<cassert>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())




int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int cnt[26];
	rep(i, 26)cnt[i]=INF;
	int n;
	cin>>n;
	rep(i,n){
		string s;
		cin>>s;
		rep(j, 26)cnt[j] = min(cnt[j],
			count(all(s),(char)('a'+j)));
	}
	rep(i, 26)cout << string(cnt[i],(char)('a'+i));
	cout<<endl;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:43:39: 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)'
   43 |                 rep(j, 26)cnt[j] = min(cnt[j],
      |                                    ~~~^~~~~~~~
   44 |                         count(all(s),(char)('a'+j)));
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:2:
/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:43:39: 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'})
   43 |                 rep(j, 26)cnt[j] = min(cnt[j],
      |                                    ~~~^~~~~~~~
   44 |                         count(all(s),(char)('a'+j)));
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:16:
/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:43:39: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   43 |                 rep(j, 26)cnt[j] = min(cnt[j],
      |                                    ~~~^~~~~~~~
   44 |                         count(all(s),(char)('a'+j)));
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~