#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
#define pb push_back
#define f first
#define s second
int main() {
int N;
cin >> N;
vector<pl> items(N);
for (int i = 0; i < N; i++) {
cin >> items[i].f >> items[i].s;
}
sort(items.begin(), items.end());
ll preB = 0;
ll maxFirst = -1e15;
ll ans = -1e15;
for (int i = 0; i < N; i++) {
maxFirst = max(maxFirst, -preB + items[i].f);
ll second = preB + items[i].s - items[i].f;
ans = max(ans, maxFirst + second);
preB += items[i].s;
}
cout << ans << endl;
}
