#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define rep(i, a, b) for(ll i = a; i < b; i++)
#define rep_(i, a, b) for(ll i = a; i > b; i--)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define vll vector<ll>
#define vvll vector<vll>
#define pll pair<ll, ll>
constexpr ll mod = 1e9+7, inf = LLONG_MAX;
void solve(){
ll n;
cin >> n;
vector<pll> a(n);
for(auto &[x, y] : a) cin >> x >> y;
sort(all(a));
ll res = LLONG_MIN, pref = 0, mn = LLONG_MAX;
for(auto &[x, y] : a){
mn = min(mn, pref-x);
pref += y;
res = max(res, pref-x - mn);
}
cout << res;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
while(t--) solve();
return 0;
}
