Language: C++

#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "string"
#include "map"
#include "unordered_map"
#include "unordered_set"
#include "iomanip"
#include "cmath"
#include "random"
#include "bitset"
#include "cstdio"
#include "numeric"
#include "cassert"
#include "ctime"

using namespace std;

constexpr long long int MOD = 1000000007;
//constexpr int MOD = 1000000007;
//constexpr int MOD = 998244353;
//constexpr long long int MOD = 998244353;
constexpr double EPS = 1e-8;

//int N, M, K, H, W, L, R;
long long int N, M, K, H, W, L, R;

const long double EPS = 1e-8;


int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	cin>>N>>K;
	vector<int>v(N);
	for(auto &i:v)cin>>i;
	for(int i=1;i<N;i++)v[i]+=v[i-1];
	long long int ans=v[K-1];
	for(int i=K;i<N;i++){
		ans=max(ans,v[i]-v[i-K]);
	}
	long double box=ans;
	box/=2;
	cout<<setprecision(20)<<box<<endl;
}


Compiler output:
a.cc:33:19: error: conflicting declaration 'const long double EPS'
   33 | const long double EPS = 1e-8;
      |                   ^~~
a.cc:28:18: note: previous declaration as 'constexpr const double EPS'
   28 | constexpr double EPS = 1e-8;
      |                  ^~~
a.cc: In function 'int main()':
a.cc:46:24: error: no matching function for call to 'max(long long int&, __gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type)'
   46 |                 ans=max(ans,v[i]-v[i-K]);
      |                     ~~~^~~~~~~~~~~~~~~~~
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:46:24: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'})
   46 |                 ans=max(ans,v[i]-v[i-K]);
      |                     ~~~^~~~~~~~~~~~~~~~~
/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:8:
/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:46:24: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   46 |                 ans=max(ans,v[i]-v[i-K]);
      |                     ~~~^~~~~~~~~~~~~~~~~