Language: C++

#include<iostream>
#include<string>
#include<vector>
#include<cmath>
#include<cstdio>
#include<utility>
#include<algorithm>
#include<map>
#include<set>
using namespace std;
#define rep(i,x,n) for(int i=x;i<n;i++)
using ll=long long;

int N,M;
int X[100],Y[100],h[100];

void gcl(int& x,int& y){
    if(x<y) swap(x,y);
    while(y>0){
        int t=x%y;
        x=y;
        y=t;
    }
    return;
}


int main(){
    string s;cin>>s;
    int k;cin>>k;
    set<string> S;
    rep(i,0,s.size()){
        rep(j,1,min(s.size()-i,k)){
            S.insert(s.substr(i,j));
        }
    }
    auto it=S.begin();
  rep(i,0,k-1) it++;
    cout<<*it<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:33:20: error: no matching function for call to 'min(std::__cxx11::basic_string<char>::size_type, int&)'
   33 |         rep(j,1,min(s.size()-i,k)){
      |                 ~~~^~~~~~~~~~~~~~
a.cc:11:34: note: in definition of macro 'rep'
   11 | #define rep(i,x,n) for(int i=x;i<n;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:33:20: note:   deduced conflicting types for parameter 'const _Tp' ('long unsigned int' and 'int')
   33 |         rep(j,1,min(s.size()-i,k)){
      |                 ~~~^~~~~~~~~~~~~~
a.cc:11:34: note: in definition of macro 'rep'
   11 | #define rep(i,x,n) for(int i=x;i<n;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:7:
/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:33:20: note:   mismatched types 'std::initializer_list<_Tp>' and 'long unsigned int'
   33 |         rep(j,1,min(s.size()-i,k)){
      |                 ~~~^~~~~~~~~~~~~~
a.cc:11:34: note: in definition of macro 'rep'
   11 | #define rep(i,x,n) for(int i=x;i<n;i++)
      |                                  ^