Language: C++

#include <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rrep(i, n) for(int i = n-1; i >= 0; --i)
#define fi first
#define se second
using namespace std;
using lint = long long;
using uint = unsigned int;
using ulint = unsigned long long;
using ldouble = long double;
using pii = pair<int, int>;
using pli = pair<lint, lint>;
using pdd = pair<double, double>;
using pld = pair<ldouble, ldouble>;
using v1i = vector<int>;
using v1li = vector<lint>;
using v2i = vector<vector<int>>;
using v2li = vector<vector<lint>>;
using v3i = vector<vector<vector<int>>>;
using v3li = vector<vector<vector<lint>>>;
using v1b = vector<bool>;
using v2b = vector<vector<bool>>;
using v3b = vector<vector<vector<bool>>>;
using v1c = vector<char>;
using v2c = vector<vector<char>>;
using v3c = vector<vector<vector<char>>>;
constexpr lint mod1 = 1e9+7;
constexpr lint mod2 = 998244353;

int main() {
  int n, k, t = 0, u = 0, a = 0;
  scanf("%d %d", &n, &k);
  char s[n];
  scanf("%s", s);
  v1i p;
  rep(i, n+1){
    if(i == n){
      if(s[i-1] == '1') p.push_back(u);
      else{
        p.push_back(t);
        p.push_back(0);
      }
      break;
    }
    if(s[i] == '1'){
      if(t > 0 || i == 0) p.push_back(t);
      t = 0;
      ++u;
    }
    else{
      if(u > 0) p.push_back(u);
      u = 0;
      ++t;
    }
  }
  vector<pii> v; t = 0; v.push_back({0, 0});
  rep(i, p.size()/2){
    v.push_back({t+p[i*2], t+p[i*2]+p[i*2+1]});
    t += p[i*2]+p[i*2+1];
  }
  k = min(k, v.size()-v.begin()-1);
  rep(i, v.size()-k) a = max(a, v[k+i].se-v[i].fi);
  printf("%d\n", a);
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:61:22: error: no match for 'operator-' (operand types are 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'std::vector<std::pair<int, int> >::iterator')
   61 |   k = min(k, v.size()-v.begin()-1);
      |              ~~~~~~~~^~~~~~~~~~
      |                    |         |
      |                    |         std::vector<std::pair<int, int> >::iterator
      |                    std::vector<std::pair<int, int> >::size_type {aka long unsigned int}
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:61:31: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
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:61:31: note:   mismatched types 'const std::complex<_Tp>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::complex<_Tp>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   'std::vector<std::pair<int, int> >::iterator' is not derived from 'const std::complex<_Tp>'
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   'std::vector<std::pair<int, int> >::iterator' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   'std::vector<std::pair<int, int> >::iterator' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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:61:31: note:   mismatched types 'const std::valarray<_Tp>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/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(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:61:31: note:   mismatched types 'const std::valarray<_Tp>' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'}
   61 |   k = min(k, v.size()-v.begin()-1);
      |                               ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution fail