#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;
#define pb push_back
#define st first
#define nd second
const ll INF = 1e18;
bool por(pair<ll, ll> a, pair<ll, ll> b) {
return a.nd < b.nd;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n;
cin >> n;
pair<ll, ll> T[n];
rep(i, n) {
cin >> T[i].nd >> T[i].st;
}
sort(T, T + n, por);
ll maks[n + 1];
maks[n] = -INF;
ll S = 0;
ll ans = 0;
for (int i = n - 1; i >= 0; i--) {
maks[i] = max(maks[i + 1], -S - T[i].nd);
S += T[i].st;
ans = max(ans, maks[i] + T[i].nd + S);
}
cout << ans << '\n';
return 0;
}
