Language: C++

#define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<stack>
#include<cstdio>
#include<cstring>
#include<bitset>
#include<unordered_map>
#include<climits>
#include<fstream>
#include<time.h>
#include<cassert>

using namespace std;
#define ll long long
#define ld long double
#define all(a) (a).begin(),(a).end()
#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define EPS (1e-13)
#define bit(n,k) ((n>>k)&1)
#define Mod = 1e9 + 7;
#define mod = 998244353;
struct H {
	ll x, y;
	bool operator<(const H& b) const {
		if (x != b.x) return x < b.x;
		return y < b.y;
	}
	bool operator>(const H& b) const {
		if (x != b.x) return x > b.x;
		return y > b.y;
	}
	bool operator==(const H& b) const { return x == b.x && y == b.y; }
	bool operator!=(const H& b) const { return (*this) != b; }
};
struct P {
	ll pos, cost;
	bool operator<(const P& b) const { return cost < b.cost; }
	bool operator>(const P& b) const { return cost > b.cost; }
};
struct B {
	ll to, cost;
};
struct E {
	ll from, to, cost;
	bool operator<(const E& b) const { return cost < b.cost; }
	bool operator>(const E& b) const { return cost > b.cost; }
};
template<typename T, typename U>
void chmin(T& a, U b) {
	if (a > b) a = b;
}
template<typename T, typename U>
void chmax(T& a, U b) {
	if (a < b) a = b;
}
template<typename T>
T max_0(T a) {
	if (a < 0) return 0;
	return a;
}
template<typename T>
T min_0(T a) {
	if (a > 0) return 0;
	return a;
}
ll read() {
	ll u;
	ll k = scanf("%lld", &u);
	return u;
}
ll gcd(ll i, ll j) {
	if (i > j) swap(i, j);
	if (i == 0) return j;
	return gcd(j % i, i);
}
ll mod_pow(ll x, ll n, ll p) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % p;
		x = x * x % p;
		n >>= 1;
	}
	return res;
}//x^n%p
ll bitcount(ll x) {
	int sum = 0;
	for (int i = 0; i < 20; i++)
		if ((1ll << i) & x) sum++;
	return sum;
}
void spsp(vector<ll>&v) {
	for (int i = 0; i < v.size(); i++) {
		printf("%lld%s", v[i], (i == v.size() - 1 ? "\n" : " "));
	}
}
/*ll fact_[200000];
ll comb(ll x, ll y, ll mod = Mod) {
	if (!fact_[0]) {
		fact_[0] = 1;
		for (int i = 1; i < 200000; i++) {
			fact_[i] = fact_[i - 1] * i % mod;
		}
	}
	if (x < y) return 0;
	return mod_pow(fact_[x], mod, mod) *
		mod_pow(fact_[x - y], mod - 2, mod) % mod *
		mod_pow(fact_[y], mod - 2, mod) % mod;
}//xCy*/
const ll Inf = 3023372036854775807;
const int inf = 1500000000;
#define int long long
//----------------------------------------------------
signed main() {
	int n;
	vector<H>a;
	cin >> n;
	int mx = -Inf, mn = Inf;
	for (int i = 0; i < n; i++) {
		int u, v;
		cin >> u >> v;
		a.push_back(H{ --u,v });
		a[i].x--;
		chmax(mx, a[i].x);
		chmin(mn, a[i].y);
	}
	int ans = 0;
	for (auto z : a) {
		chmax(ans, max(0ll, mn - mx) + z.y - z.x);
	}
	vector<H>v;
	rep(i, n) {
		int c = max(0ll, mn - a[i].x);
		int d = max(0ll, a[i].y - mx);
		v.push_back(H{ d, -c });
	}
	sort(all(v));
	int w = inf;
	rep(i, n) {
		auto z = v[i];
		z.y = -z.y;
		if (i) chmax(ans, w + z.x);
		chmin(w, z.y);
	}
	cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:30: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                              ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected ';' before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected ')' before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:28:23: note: to match this '('
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                       ^
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:143:13: error: 'i' was not declared in this scope
  143 |         rep(i, n) {
      |             ^
a.cc:28:46: note: in definition of macro 'rng'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                              ^
a.cc:143:9: note: in expansion of macro 'rep'
  143 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:30: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                              ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected ';' before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected primary-expression before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~
a.cc:123:13: error: expected ')' before 'long'
  123 | #define int long long
      |             ^~~~
a.cc:28:39: note: in expansion of macro 'int'
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                                       ^~~
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~
a.cc:28:23: note: to match this '('
   28 | #define rng(i,a,b) for(int i=int(a);i<int(b);i++)
      |                       ^
a.cc:29:18: note: in expansion of macro 'rng'
   29 | #define rep(i,b) rng(i,0,b)
      |                  ^~~
a.cc:150:9: note: in expansion of macro 'rep'
  150 |         rep(i, n) {
      |         ^~~