Language: C++

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
#define endl '\n'
#define ll long long
#define pi pair<int, int>
#define f first
#define s second

const int mxn = 100002;
int n, k;
ll a[mxn];
ll s[2][mxn];

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> k;
	
	for(int i = 1; i <= n; i++) cin >> a[i];
	
	for(int t = 0; t < 2; t++){
		for(int i = 1; i <= n; i++){
			s[t][i] = max(0, a[i]) + s[t][i - 1];
		}
		reverse(a, a + n + 2);
	}
	reverse(s[1], s[1] + n + 2);
	
	for(int i = 1; i <= n; i++) a[i] += a[i - 1];
	
	ll ret = 0xcfcfcfcfcfcfcfcf;
	for(int i = 1; i <= n - k + 1; i++){
		ret = max(ret, s[0][i - 1] + s[1][i + k] + max(0, a[i + k - 1] - a[i - 1]));
	}
	
	cout << ret << endl;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:26:38: error: no matching function for call to 'max(int, long long int&)'
   26 |                         s[t][i] = max(0, a[i]) + s[t][i - 1];
      |                                   ~~~^~~~~~~~~
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:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:26:38: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   26 |                         s[t][i] = max(0, a[i]) + s[t][i - 1];
      |                                   ~~~^~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: 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:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:26:38: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   26 |                         s[t][i] = max(0, a[i]) + s[t][i - 1];
      |                                   ~~~^~~~~~~~~
a.cc:36:63: error: no matching function for call to 'max(int, long long int)'
   36 |                 ret = max(ret, s[0][i - 1] + s[1][i + k] + max(0, a[i + k - 1] - a[i - 1]));
      |                                                            ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:36:63: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   36 |                 ret = max(ret, s[0][i - 1] + s[1][i + k] + max(0, a[i + k - 1] - a[i - 1]));
      |                                                            ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:36:63: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   36 |                 ret = max(ret, s[0][i - 1] + s[1][i + k] + max(0, a[i + k - 1] - a[i - 1]));
      |                                                            ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~