#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<class A> ostream& operator<<(ostream &cout, vector<A> const &v) {cout << "["; for(int i = 0; i < v.size(); i++) {if (i) cout << ", "; cout << v[i];} return cout << "]";};
template<class A, class B> ostream& operator<<(ostream &cout, const pair<A,B> &x) {return cout << "(" <<x.first << ", " << x.second << ")";};
template <class T> void pv(T a, T b) {cerr << "["; for (T i = a; i != b; ++i) cerr << *i << " "; cerr << "]\n";}
void _print() {cerr << "]\n";}
template <class T, class... V> void _print(T t, V... v) {cerr << t; if (sizeof...(v)) cerr << ", "; _print(v...);}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#define fi first
#define se second
#define SZ(x) (int)((x).size())
#define pii pair<ll,ll>
pii a[500000];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
map<ll,ll> ma, rma;
for (int q = 0; q < n; q++) {
cin >> a[q].fi >> a[q].se;
ma[a[q].fi] = 0;
}
sort(a, a+n);
int cur = 1;
auto it = ma.begin();
while (it != ma.end()) {
rma[cur] = it->fi;
it->se = cur++;
it++;
}
vector<ll> pref(cur);
int ptr = 0;
int upd = 1;
while (ptr < n) {
int pt = ptr;
ll tot = 0;
while (pt < n && a[pt].fi == a[ptr].fi) {
tot += a[pt].se;
pt++;
}
pref[upd] = pref[upd-1]+tot;
upd++;
ptr = pt;
}
multiset<ll> stuff;
for (int q = 1; q < cur; q++) {
stuff.insert(pref[q]-rma[q]);
}
ll ans = LLONG_MIN;
for (int q = 0; q < cur-1; q++) {
ans = max(ans, *stuff.rbegin()+rma[q+1]-pref[q]);
stuff.erase(stuff.find(pref[q+1]-rma[q+1]));
}
cout << ans << "\n";
return 0;
}
