Language: C++

#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include<ext/pb_ds/tag_and_trait.hpp>
#define BEGIN ios_base::sync_with_stdio(0);cin.tie(0)
#define END return EXIT_SUCCESS
#define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
#define DOWN(I,A,B) for((I)=(A);(I)>=(B);(I)--)
#define IN(P) std::cin>>(P)
#define IN2(P1,P2) std::cin>>(P1)>>(P2)
#define IN3(P1,P2,P3) std::cin>>(P1)>>(P2)>>(P3)
#define INS(I,N,V) UP(I,0,N) std::cin>>V[I]
#define OUT(P) std::cout<<P<<std::endl
#define OUT2(P1,P2) std::cout<<P1<<" "<<P2<<std::endl
#define OUT3(P1,P2,P3) std::cout<<P1<<" "<<P2<<" "<<P3<<std::endl
#define OUTS(I,N,V) UP(I,0,N) std::cout<<V[i]<<std::endl
#define ALL(C) (C).begin(),(C).end()
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
typedef long long ll;
typedef unsigned int ui;
typedef unsigned long long ull;
using namespace std;
using namespace __gnu_pbds;
long i,j,k;
string S;
long K;
long N;
inline void solve(){
  IN2(S,K);
  N=S.size();
  UP(i,0,S-1){
    if(S[i]!='1'){
      OUT(S[i]);
      return;
    }
  }
  OUT(1);
}

int main(int argc,char**argv){
  BEGIN;
  solve();
  END;
}


Compiler output:
a.cc: In function 'void solve()':
a.cc:36:11: error: no match for 'operator-' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   36 |   UP(i,0,S-1){
      |          ~^~
      |          | |
      |          | int
      |          std::string {aka std::__cxx11::basic_string<char>}
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const valarray<_Tp>&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:36:12: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   36 |   UP(i,0,S-1){
      |            ^
a.cc:7:37: note: in definition of macro 'UP'
    7 | #define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
      |                                     ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1197 | _DEFINE_BINARY_OPERATOR