#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimize("-Ofast")
#include <bits/stdc++.h>
#include <algorithm>
#include <iostream>
#include <vector>
#include <limits>
#include <cmath>
#include <stack>
#include <queue>
#include <map>
#include <math.h>
using namespace std;
using ll = long long;
/*
void solve(){
ll n;
cin >> n;
vector<pair<ll, ll>> list_n(n, pair<ll, ll>{0, 0});
for(ll i = 0; i < n; i++){
cin >> list_n[i].first;
cin >> list_n[i].second;
}
sort(list_n.begin(), list_n.end());
ll curr_max = -1E15 - 5;
for(ll i = 0; i < n; i++){
ll start = list_n[i].first;
ll curr = 0;
for(ll j = i; j < n; j++){
curr += list_n[j].second;
curr_max = max(curr_max, curr - list_n[j].first + start);
if(curr - list_n[j].first + start == 4232545716) {
cout << i << " " << j << endl;
}
}
}
cout << curr_max << endl;
}
*/
void solve() {
ll n;
cin >> n;
ll curr_max = 0;
vector<pair<ll, ll>> list_n(n, pair<ll, ll>{0, 0});
for (ll i = 0; i < n; i++) {
cin >> list_n[i].first;
cin >> list_n[i].second;
curr_max = max(list_n[i].second, curr_max);
}
sort(list_n.begin(), list_n.end());
/*for (ll i = 0; i < n; i++) {
cout << list_n[i].first << " " << list_n[i].second << endl;
}*/
ll curr_min = 0;
ll curr = 0;
ll curr_pos = 0;
for(ll i = 0; i < n; i++){
if(i == 0){
curr = -list_n[i].first;
curr_pos = list_n[i].second - list_n[i].first;
curr_min = curr;
curr_max = max(curr_max, curr_pos - curr_min);
continue;
}
curr += list_n[i - 1].first + list_n[i - 1].second - list_n[i].first;
curr_pos += list_n[i].second + list_n[i - 1].first - list_n[i].first;
curr_min = min(curr_min, curr);
curr_max = max(curr_max, curr_pos - curr_min);
}
//cout << curr_max;
cout << curr_max << endl;
}
int main(){
ios_base::sync_with_stdio(false);
cout.tie(0);
cin.tie(0);
ll t = 1;
while(t--){
solve();
}
}
