Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

#define int ll
#define REP(i,n) for (int i = 0; i < (n); ++i)
#define FORE(i, s, n) for (int i = (s); i <= (int)(n); i++)
#define debug(x) cerr << #x << ": " << x << '\n'
#define hyphen() cerr << "--\n"

#define ALL(vec) (vec).begin(), (vec).end()
#define REVALL(vec) (vec).rbegin(), (vec).rend()

#define fst first
#define pb push_back

const int MOD = (int)1e9 + 7;

// 答えを見たよ。
int calc(int N, int K, int b) {
    int p = N / b;
    int r = N % b;

    // a % b >= K であるようなaの種類
    // (0 <= a <= N)
    int ans = p * max(0, b - K) + max(0, r - K + 1);

    // 0 % b => K であるものをカウントしてしまっているので引く
    if (K == 0) {
        ans -= 1;
    }

    return ans;
}

signed main() {
    int N, K;

    cin >> N >> K;

    int ans = 0;
    FORE(b, 1, N) {
        ans += calc(N, K, b);
    }

    cout << ans << endl;
    return 0;
}


Compiler output:
a.cc: In function 'll calc(ll, ll, ll)':
a.cc:27:22: error: no matching function for call to 'max(int, ll)'
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 1);
      |                   ~~~^~~~~~~~~~
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:27:22: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'll' {aka 'long long int'})
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 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:
/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:27:22: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 1);
      |                   ~~~^~~~~~~~~~
a.cc:27:38: error: no matching function for call to 'max(int, ll)'
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 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:27:38: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'll' {aka 'long long int'})
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 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:27:38: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   27 |     int ans = p * max(0, b - K) + max(0, r - K + 1);
      |                                   ~~~^~~~~~~~~~~~~~