#include <bits/stdc++.h>
using namespace std;
#define kien long long
#define int int64_t
#define pb push_back
#define FOR(i, a, b) for (int i = a;i <= b; i++)
#define FORD(i, a, b) for (int i = a;i >= b; i--)
#define pii pair<int, int>
#define dembit(a) __builtin_popcountll(a)
#define task "kien"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define debug(x) cout << x << " "
#define down cout << "\n"
const kien MOD = 1e18 + 7;
const int NTEST = 100;
const int Million = 1e6;
const int MXN = 5e5 + 5;
const int INF = 1e9;
mt19937 rd(chrono::high_resolution_clock::now().time_since_epoch().count());
kien rand(kien l, kien r) {
assert(l <= r);
return uniform_int_distribution<kien>(l, r)(rd);
}
kien n, k, m, u, v, h, pre[MXN];
kien maxx, minn, sum, vtr, s, t, r, x, l, timer, ans, add;
pii a[MXN];
//vector <pii> dp[MXN];
map <kien, int> pp;
bool ktr (int mid) {
// pp.clear();
maxx = a[1].first;
FOR (i, 1, n - 1) {
if (pre[i] - a[i].first >= mid - maxx) return true;
}
return false;
}
void tmp() {
FOR (i, 1, n) {
pre[i] = pre[i - 1] + a[i].second;
}
int l = 0, r = sum;
int kq = 0;
while (l <= r) {
int mid = (l + r) >> 1;
if (ktr(mid)) {
l = mid + 1;
kq = mid;
}
else {
r = mid - 1;
}
}
cout << kq;
}
void solve() {
cin >> n;
FOR (i, 1, n) {
cin >> a[i].first >> a[i].second;
// sum += a[i].second;
// maxx = max(maxx, a[i].first); minn = min(minn, a[i].first);
}
sort (a + 1, a + 1 + n);
minn = MOD; ans = -MOD;
FOR (i, 1, n) {
minn = min(minn, sum - a[i].first);
sum += a[i].second;
ans = max(ans, sum - a[i].first - minn);
}
cout << ans;
}
main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
if (fopen(task".inp", "r")) {
fin(task); fou(task);
}
int tt = 1; // cin >> tt;
while(tt--) {
solve();
}
cerr << "\n" << 1.0 * clock() / CLOCKS_PER_SEC << "s ";
}
