Language: C++

#include <bits/stdc++.h>
#define ll long long 
using namespace std;

struct interval {
  ll s, f;
  interval(ll s, ll f) : s(s), f(f) { }
};

bool compare_f(const interval &x, const interval &y) {
  return x.f < y.f;
}

ll count_interval(const vector<interval>& vec){
  ll result=0;
  ll pre_f = vec.front().s-10;
  for(auto& v:vec){
    result += max(0, v.f - max(v.s-1LL, pre_f));
    pre_f = v.f;
  }
  return result;
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(0);
  ll N,X,D;
  cin >> N >> X >> D;
  ll sum=0;
  if(D==0){
    if(X==0) cout << 1 << endl;
    else cout << N+1 << endl;
    return 0;
  }
  if(D<0){
    D = -D;
    X = -X;
  }
  map<int,vector<interval> > m;
  set<int> kXD;
  for(int k=0;k<=N;k++){
    ll Imin = k*(k-1)/2+k*X/D;
    ll Imax = (2*N-k-1)*k/2+k*X/D;
    m[(int)k*X%D].push_back(interval(Imin,Imax));
    kXD.insert((int)k*X%D);
  }
  for(auto d:kXD){
    if(m[d].empty()) continue;
    sort(m[d].begin(),m[d].end(),compare_f);
    sum += count_interval(m[d]);
  }
  cout << sum << endl;
  return 0;
}


Compiler output:
a.cc: In function 'long long int count_interval(const std::vector<interval>&)':
a.cc:18:18: error: no matching function for call to 'max(int, long long int)'
   18 |     result += max(0, v.f - max(v.s-1LL, pre_f));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:18:18: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   18 |     result += max(0, v.f - max(v.s-1LL, pre_f));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:18:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   18 |     result += max(0, v.f - max(v.s-1LL, pre_f));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~