Language: C++

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

#define rep(i, j) for (int i = 0; i < j; i++)
#define all(obj) (obj).begin(), (obj).end()
#define rall(obj) (obj).rbegin(), (obj).rend()
typedef long long int ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;

template<class T,class U> void chmax(T& a, U b) {if(a<b)a=b;}
template<class T,class U> void chmin(T& a ,U b) {if(b<a)a=b;}

int main() {

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.precision(10);
    cout << fixed;

    int n;
    cin >> n;
    vector<pair<ll, ll>> lr(n);
    rep(i, n) {
        cin >> lr[i].first >> lr[i].second;
        lr[i].second++;
    }

    ll lmax = 0, rmin = (1 << 30);
    rep(i, n) {
        chmax(lmax, lr[i].first);
        chmin(rmin, lr[i].second);
    }

    multiset<ll> s, ss;
    vector<pair<ll, ll>> ab(n);
    rep(i, n) {
        ab[i].first  = max(0LL, lr[i].second - lmax);
        ab[i].second = max(0LL, rmin -  lr[i].first);

        // cout << " -- " << i << " " << ab[i].first << " " << ab[i].second << endl;
        s.insert(ab[i].first);
        ab[i].second *= -1;
    }

    ll ans = 0;
    rep(i, n) chmax(ans, max(0, rmin - lmax) + lr[i].second - lr[i].first);
    // cout << ans << endl;

    sort(all(ab));
    rep(i, n - 1) {
        auto it = s.find(ab[i].first);
        if (it != s.end()) s.erase(it);
        ss.insert(-ab[i].second);
        // cout << s.size() << endl;
        chmax(ans, *ss.begin() + *s.begin());
        // cout << i << " " << -ab[i].second << " " << *s.begin() << " " << ans << endl;
    }

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


Compiler output:
a.cc: In function 'int main()':
a.cc:49:29: error: no matching function for call to 'max(int, ll)'
   49 |     rep(i, n) chmax(ans, max(0, rmin - lmax) + lr[i].second - lr[i].first);
      |                          ~~~^~~~~~~~~~~~~~~~
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:49:29: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'll' {aka 'long long int'})
   49 |     rep(i, n) chmax(ans, max(0, rmin - lmax) + lr[i].second - lr[i].first);
      |                          ~~~^~~~~~~~~~~~~~~~
/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:49:29: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   49 |     rep(i, n) chmax(ans, max(0, rmin - lmax) + lr[i].second - lr[i].first);
      |                          ~~~^~~~~~~~~~~~~~~~