//#pragma optimize("Ofast")
//#pragma optimize("unroll-loops")
//#pragma target("avx,avx2")
#include <iostream>
#include <cmath>
#include <algorithm>
#include <stdio.h>
#include <cstdint>
#include <cstring>
#include <string>
#include <cstdlib>
#include <vector>
#include <bitset>
#include <map>
#include <queue>
#include <ctime>
#include <stack>
#include <set>
#include <list>
#include <random>
#include <deque>
#include <functional>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <complex>
#include <numeric>
#include <cassert>
#include <array>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <thread>
typedef long long ll;
typedef long double ld;
using namespace std;
#define el '\n'
#define ff first
#define ss second
#define pb push_back
#define popb pop_back
#define point pair <ll, ll>
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
const ll N = 5e5 + 10;
const ll INF = 2e18 + 10;
const ll inf = 2e9 + 10;
ll t[4 * N], lazy[4 * N];
void push(ll v) {
t[v << 1] += lazy[v];
t[v << 1 | 1] += lazy[v];
lazy[v << 1] += lazy[v];
lazy[v << 1 | 1] += lazy[v];
lazy[v] = 0;
}
void upd(ll v, ll tl, ll tr, ll l, ll r, ll val) {
if (l > tr || r < tl)
return;
if (l <= tl && r >= tr) {
t[v] += val;
lazy[v] += val;
return;
}
push(v);
ll tm = (tl + tr) >> 1;
upd(v << 1, tl, tm, l, r, val);
upd(v << 1 | 1, tm + 1, tr, l, r, val);
t[v] = max(t[v << 1], t[v << 1 | 1]);
}
ll get(ll v, ll tl, ll tr, ll l, ll r) {
if (l > tr || r < tl)
return -INF;
if (l <= tl && r >= tr)
return t[v];
push(v);
ll tm = (tl + tr) >> 1;
return max(get(v << 1, tl, tm, l, r),
get(v << 1 | 1, tm + 1, tr, l, r));
}
void solve() {
ll n;
cin >> n;
vector <point> events(n);
for (ll i = 0; i < n; i++)
cin >> events[i].ff >> events[i].ss;
sort(all(events));
ll ans = -INF;
for (ll i = 0; i < n; i++) {
upd(1, 1, n, i + 1, i + 1, events[i].ff);
upd(1, 1, n, 1, i + 1, events[i].ss);
ans = max(ans, get(1, 1, n, 1, i + 1) - events[i].ff);
}
cout << ans << el;
return;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int tests = 1;
//cin >> tests;
while (tests--)
solve();
return 0;
}
