#include <iostream>
#include <vector>
#include <tuple>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <cmath>
#include <array>
#include <random>
#include <climits>
#include <cassert>
#include <algorithm>
using namespace std;
template<typename A, typename B> ostream& operator << (ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator << (ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) { os << sep << x, sep = ", "; } return os << '}'; }
void D_out() { cerr << endl; }
template<typename Head, typename... Tail> void D_out(Head H, Tail... T) { cerr << ' ' << H; D_out(T...); }
#ifdef DEBUG
#define D(...) cerr << '(' << #__VA_ARGS__ << "):", D_out(__VA_ARGS__)
#else
#define D(...)
#endif
//#define int long long
#define ll long long
#define ld long double
#define f first
#define s second
#define sz(x) ((int) x.size())
#define all(x) (x).begin(), (x).end()
const ll MOD = 1e9 + 7;
const ll INF = 1e18;
int n;
ll ans, tmp;
vector<pair<ll, ll>> art;
void solve() {
cin >> n;
for (int i = 0; i < n; i++) {
ll x, y; cin >> x >> y;
art.push_back({x, y});
}
art.push_back({0, 0});
sort(art.begin(), art.end());
tmp = 1e12;
for (int i = 1; i <= n; i++) {
art[i].s += art[i - 1].s;
tmp = min(tmp, art[i - 1].s - art[i].f);
ans = max(ans, art[i].s - art[i].f - tmp);
}
cout << ans << "\n";
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int t = 1; //cin >> t;
for (int tc = 1; tc <= t; tc++) {
//cout << "Case #" << tc << ": ";
solve();
}
}
