#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define ff first
#define ss second
#define pii pair<int,int>
#define endl '\n'
const int inf = 1e18;
const int N = 2e5+5;
inline void test_case() {
int n, ans = -inf, val = -inf, pref = 0;
cin >> n;
vector<pii> a;
for (int i = 0; i < n; i++) {
int x, y; cin >> x >> y;
a.pb({x,y});
}
sort(a.begin(),a.end());
for (int i = 0; i < n; i++) {
val = max(val,a[i].ff-pref);
pref += a[i].ss;
ans = max(ans,val+pref-a[i].ff);
}
cout << ans << endl;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int T = 1;
// cin >> T;
while (T--) test_case();
}
