#include <bits/stdc++.h>
//~ #ifndef EVAL
//~ #include "grader.cpp"
//~ #endif
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
#define pb push_back
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define sz(v) int((v).size())
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl '\n'
int mod = 1e9+7;
ll modulo(ll a) {
return ((a % mod) + mod) % mod;
}
ll add(ll a, ll b) {
return modulo(a + b);
}
ll mult(ll a, ll b) {
return modulo(a * b);
}
ll binpow(ll a, ll b) {
ll res = 1;
while (b) {
if (b&1) {
res = mult(res, a);
}
a = mult(a, a);
b >>= 1;
}
return res;
}
void solve() {
int n;
cin >> n;
vector <pll> a(n+1);
for (int i = 1; i <= n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a.begin()+1, a.end());
vector <ll> pref(n+1), saizu(n+1);
for (int i = 1; i <= n; i++) {
saizu[i] = a[i].first;
pref[i] = pref[i-1] + a[i].second;
}
ll ans = -9e18, mx = 0;
for (int i = 1; i <= n; i++) {
mx = max(mx, saizu[i]-pref[i-1]);
ans = max(ans, pref[i]-saizu[i]+mx);
}
cout << ans;
}
int main() {
do_not_disturb
int t = 1;
//~ cin >> t;
while (t--) {
solve();
}
return 0;
}
