#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T>
bool chmax(T &a, T b) { return a < b ? (a = b, true) : false; }
template<class T>
bool chmin(T &a, T b) { return b < a ? (a = b, true) : false; }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U>
void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T>
void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L) == R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 300010;
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int n;
cin >> n;
vector<pair<ll,ll>> art(n);
for (auto &[sz, val] : art)
cin >> sz >> val;
art.pb(0, 0);
sort(AI(art));
ll mx = 0, res = 0, sum = 0;
for (int i = 0;i <= n;++i) {
auto [sz, val] = art[i];
ll nxsz = i == n ? 0 : art[i+1].first;
sum += val;
chmax(res, sum - sz + mx);
chmax(mx, nxsz - sum);
chmax(res, val);
}
assert(res > 0);
cout << res << '\n';
}
