Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define ll long long

int main() {
    int n;
    ll l,r;
    cin>>n;
    vector<pair<ll,ll>> v;
    for(int i=0;i<n;i++){
        cin>>l>>r;
        v.emplace_back(l,r);
    }
    sort(v.begin(),v.end());
    int l_ind=0,r_ind=0;
    for(int i=1;i<n;i++){
        if(v[i].first>v[l_ind].first) l_ind=i;
        if(v[i].second<v[r_ind].second) r_ind=i;
    }
    ll mx=0;
    for(int i=0;i<n;i++){
        if(i!=l_ind && i!=r_ind){
            mx=max(mx,v[i].second-v[i].first+1);
        }
    }
    ll r_val[n];
    r_val[n-1]=v[n-1].second;
    for(int i=n-2;i>=0;i--){
        r_val[i]=min(v[i].second, r_val[i+1]);
    }
    ll res=0;
    if(l_ind==r_ind){
        res=mx+v[l_ind].second-v[l_ind].first+1;
    }
    else{
        res=mx;
        for(int i=r_ind;v[i].first<=v[r_ind].second && i<n;i++){
            if(i<n-1){
                res=max(res,v[r_ind].second-v[i].first+1+max(0,r_val[i+1]-v[l_ind].first+1));
            }
            else res=max(res,mx+v[r_ind].second-v[i].first+1);
        }
    }
    cout<<res<<"\n";
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:42:61: error: no matching function for call to 'max(int, long long int)'
   42 |                 res=max(res,v[r_ind].second-v[i].first+1+max(0,r_val[i+1]-v[l_ind].first+1));
      |                                                          ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 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:42:61: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   42 |                 res=max(res,v[r_ind].second-v[i].first+1+max(0,r_val[i+1]-v[l_ind].first+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,
                 from a.cc:3:
/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:42:61: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   42 |                 res=max(res,v[r_ind].second-v[i].first+1+max(0,r_val[i+1]-v[l_ind].first+1));
      |                                                          ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~