Language: C++

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

const int INF = 1001001001;

int main(){
  ll n;
  cin >> n;
  ll maxl = 0,minr = 10e9,distmax = 0,case1 = 0,case2 = 0;
  vector<pair<int,int>> lr;
  for(int i=0;i<n;i++){
    ll l; cin >> l;
    ll r; cin >> r;
    maxl = max(l,maxl);
    minr = min(r,minr);
    lr.push_back(make_pair(l,r));
    distmax = max(distmax,r-l);
  }

  //右端が一番左側にあるpairと左端が一番右がわにあるpairを同じ集合に含む
  case1 = minr - maxl + 1 + distmax + 1;

  //別々の集合に含まれる
  {
    for(int i=0;i<n;i++){
      lr.at(i).first = max(minr-lr.at(i).first + 1,0);
      lr.at(i).second = max(lr.at(i).second-maxl + 1,0);
    }
    sort(lr.begin(),lr.end());
    ll mina = INF,minb = INF;
    for(int i=0;i<n-1;i++){
      mina = lr.at(i+1).first;
      minb = min(minb,lr.at(i).second);
      case2 = max(case2,mina + minb);
    }
  }
  cout << max(case1,case2) << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:27:27: error: no matching function for call to 'max(ll, int)'
   27 |       lr.at(i).first = max(minr-lr.at(i).first + 1,0);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
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:27:27: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   27 |       lr.at(i).first = max(minr-lr.at(i).first + 1,0);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:27:27: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   27 |       lr.at(i).first = max(minr-lr.at(i).first + 1,0);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:28:28: error: no matching function for call to 'max(ll, int)'
   28 |       lr.at(i).second = max(lr.at(i).second-maxl + 1,0);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:28:28: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   28 |       lr.at(i).second = max(lr.at(i).second-maxl + 1,0);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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
/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:28:28: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   28 |       lr.at(i).second = max(lr.at(i).second-maxl + 1,0);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:34:17: error: no matching function for call to 'min(ll&, int&)'
   34 |       minb = min(minb,lr.at(i).second);
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:34:17: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   34 |       minb = min(minb,lr.at(i).second);
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:34:17: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   34 |       minb = min(minb,lr.at(i).second);
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~