Language: C++

#pragma GCC optimize ("O3")
#include <bits/stdc++.h>
#define DEBUG true
#ifdef ONLINE_JUDGE
#undef DEBUG
#define DEBUG false
#endif 

using namespace std;

#define MAXN ((int)2e5+5)
#define MOD ((int)1e9 + 7)
#define INF ((int)1e9 + 9)
#define ll long long
#define _ << " " <<
#define CLEAR(a, b) memset(a, b, sizeof(a))
#define TRACE(x) if(DEBUG) cerr << #x << " = " << x << endl;
#define TRACE2(x,y) if(DEBUG) cerr << #x << " = " << x << " | " << #y << " = " << y << endl;
#define pb push_back
#define all(x) x.begin(), x.end()
#define endl "\n"
#define pii pair<int,int>
#define mid ((l+r)/2)

int n;
vector <int> v;
int ans;

int main()
{
	ios_base::sync_with_stdio(false);cin.tie(0);
	cin >> n;
	v.resize(n);

	for (int i = 0; i < n; ++i)
		cin >> v[i];

	sort(all(v));

	for (int i = 0; i < n; ++i)
	{
		for (int j = i+1; j < n; ++j)
		{
			int minval = v[j] - v[i];
			int maxval = v[j] + v[i] - 1;

			auto p1 = upper_bound(all(v), minval); // first > minval
			auto p2 = upper_bound(all(v), maxval); // first non working index

			int i1 = max(p1 - v.begin(), j+1);
			int i2 = p2 - v.begin();

			// TRACE2(i1,i2);
			ans += (i2-i1);
		}
	}

	cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:50:37: error: no matching function for call to 'max(__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type, int)'
   50 |                         int i1 = max(p1 - v.begin(), j+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:2:
/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:50:37: note:   deduced conflicting types for parameter 'const _Tp' ('long int' and 'int')
   50 |                         int i1 = max(p1 - v.begin(), j+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:50:37: note:   mismatched types 'std::initializer_list<_Tp>' and 'long int'
   50 |                         int i1 = max(p1 - v.begin(), j+1);
      |                                  ~~~^~~~~~~~~~~~~~~~~~~~~