Language: C++

#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<(n); ++i)
#define rep1(i,n) for(int i=1; i<=(n); ++i)
#define repi(i,a,b) for(int i=a; i<=(b); ++i)
#define rrep(i,n) for(int i=(n-1); i>=0; --i)
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define mp make_pair
#define to_s to_string
#define sz(v) (int)v.size()
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define pr(x) cout<<(x)<<'\n'
#define debug(x) cout << #x << ": " << (x) << '\n'
#define yes "Yes"
#define no "No"
using ll = long long;
using namespace std;
typedef pair<int,int> P;
struct aaa{aaa(){ cin.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(20);};}aaaaaaa;
int MOD = 1e9 + 7;
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return (a*b)/gcd(a,b);}
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

ll N,K;
int main(){
    cin >> N >> K;
    vector<ll> V(N);
    rep(i,N) cin >> V[i];
    ll ans = 0;
    rep(A,100) rep(B,100) rep(C,100) if(A+B+C <= K && A+B >= C){
        vector<ll> item = {};
        rep(i,A) item.pb(V[i]);
        rep(i,B) item.pb(V[sz(V)-1-i]);
        sort(ALL(item));
        ans = max(ans,accumulate(item.begin()+C,item.end(),0));
    }
    pr(ans);
}

Compiler output:
a.cc: In function 'int main()':
a.cc:38:18: error: no matching function for call to 'max(ll&, int)'
   38 |         ans = max(ans,accumulate(item.begin()+C,item.end(),0));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included 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_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:38:18: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   38 |         ans = max(ans,accumulate(item.begin()+C,item.end(),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:
/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:38:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   38 |         ans = max(ans,accumulate(item.begin()+C,item.end(),0));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~