Language: C++

#include <iostream>
#include<iomanip>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
#include <queue>
#define INF 1e9+7
#define rep(i,m,n) for(int i=m;i<n;i++)
#define mrep(i,m,n) for(int i=m;i>n;i--)
#define NO cout<<"NO"<<endl;
#define YES cout << "YES"<<endl;
#define No cout << "No"<<endl;
#define Yes cout << "Yes"<<endl;
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;


//(int)'a'は97 (int)'A'は65 (int)'1'は49
//おまじない




int main() {

	int  k;
	string s, sub;
	vector<string> ss;
	cin >> s >> k;
	int m = min(k, s.size());

	for (int i = 1; i <=m ; i++) {
		for (int j = 0; j < s.size() - i; j++) {
			sub = s.substr(j, i);
			ss.push_back(sub);
		}
	}

	unique(ss.begin(), ss.end());

	cout << ss[k - 1] << endl;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:32:20: error: no matching function for call to 'min(int&, std::__cxx11::basic_string<char>::size_type)'
   32 |         int m = min(k, s.size());
      |                 ~~~^~~~~~~~~~~~~
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:32:20: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'})
   32 |         int m = min(k, s.size());
      |                 ~~~^~~~~~~~~~~~~
/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:3:
/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:32:20: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   32 |         int m = min(k, s.size());
      |                 ~~~^~~~~~~~~~~~~
a.cc:41:15: warning: ignoring return value of '_FIter std::unique(_FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<__cxx11::basic_string<char>*, vector<__cxx11::basic_string<char> > >]', declared with attribute 'nodiscard' [-Wunused-result]
   41 |         unique(ss.begin(), ss.end());
      |         ~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:891:5: note: declared here
  891 |     unique(_ForwardIterator __first, _ForwardIterator __last)
      |     ^~~~~~