#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define sz(a) (long long) a.size()
#define endl '\n'
const long long INF = 1e18, MOD = 1e9+7;
void test_case() {
int n;
cin >> n;
vector<int> a;
map<int,int> mp;
for (int i = 0; i < n; i++) {
int s, v;
cin >> s >> v;
if (!mp.count(s)) {
a.push_back(s);
}
mp[s] += v;
}
sort(a.begin(), a.end());
set<pair<int,int>> s;
vector<int> value(sz(a));
int cur = 0;
for (int i = 0; i < sz(a); i++) {
cur += mp[a[i]];
s.insert({cur - a[i], i});
value[i] = cur - a[i];
}
int ans = 0;
for (int i = 0; i < sz(a); i++) {
ans = max(ans, (*s.rbegin()).fi + a[i] - (i? value[i - 1] + a[i - 1] : 0));
auto it = s.find({value[i], i});
assert(it != s.end());
s.erase(it);
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int tt = 1;
//cin >> tt;
while (tt--) {
test_case();
}
return 0;
}
