Language: C++

#include<iostream>
#include<iomanip>
#include<map>
#include<unordered_map>
#include<set>
#include<unordered_set>
#include<vector>
#include<array>
#include<string>
#include<stack>
#include<queue>
#include<algorithm>
#include<cassert>
#include<functional>
#include<random>
#include<complex>
#include<bitset>
#include<chrono>
//#include<boost/multiprecision/cpp_int.hpp>
#define int int64_t
#define uint uint64_t
#define REP(i, a, b) for (int64_t i = (int64_t)(a); i < (int64_t)(b); i++)
#define rep(i, a) REP(i, 0, a)
#define SZ(X) ((int64_t)((X).size()))
#define ITR(x, a) for (auto x = a.begin(); x != a.end(); x++)
#define ALL(a) (a.begin()), (a.end())
#define HAS(a, x) (a.find(x) != a.end())
#define Min(x) *min_element(ALL(x))
#define Max(x) *max_element(ALL(x))
#define Unique(L) (L.erase(unique(ALL(L)), L.end()))
#define intmax (std::numeric_limits<int64_t>::max() / 4)
#define doublemax (std::numeric_limits<double>::max() / 4)
using namespace std;
//typedef boost::multiprecision::cpp_int bigint;
const double EPS = 1e-9;
const double PI = acos(-1.0);

//sort(ALL(v),greater<int>());


signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N, K;
	cin >> N >> K;
	vector<int>a(N);
	rep(i, N)cin >> a[i];

	int ksum = 0;
	rep(i, K)ksum += a[i];
	int ksummax = ksum, ksmindex = 0;
	REP(i, K, N) {
		ksum += a[i];
		ksum -= a[i - K];
		if (ksummax < ksum) {
			ksummax = ksum;
			ksmindex = i-K+1;
		}
	}

	int ans = max(ksummax,0);
	rep(i, ksmindex)if (0 < a[i])ans += a[i];
	REP(i, ksmindex + K, N)if (0 < a[i])ans += a[i];
	cout << ans << endl;


	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:62:22: error: no matching function for call to 'max(int64_t&, int)'
   62 |         int ans = max(ksummax,0);
      |                   ~~~^~~~~~~~~~~
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:62:22: note:   deduced conflicting types for parameter 'const _Tp' ('long int' and 'int')
   62 |         int ans = max(ksummax,0);
      |                   ~~~^~~~~~~~~~~
/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:12:
/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:62:22: note:   mismatched types 'std::initializer_list<_Tp>' and 'long int'
   62 |         int ans = max(ksummax,0);
      |                   ~~~^~~~~~~~~~~