#include<bits/stdc++.h>
//#include <grader.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define ll long long
#define ld long double
#define st first
#define nd second
#define pb push_back
#define INF INT_MAX
using namespace std;
const int N = 5e5 + 10;
pll a[N];
ll b[N], c[N], qs[N], qss[N];
void solve() {
int n; cin >> n;
for (int i = 1; i <= n; ++i) cin >> a[i].st >> a[i].nd;
sort(a+1, a+n+1);
for (int i = 1; i <= n; ++i) b[i] = -(a[i].st - a[i-1].st) + a[i].nd;
for (int i = 1; i <= n; ++i) b[i] += b[i-1];
c[n] = b[n];
for (int i = n-1; i >= 1; --i) c[i] = max(c[i+1], b[i]);
ll ans = 0;
for (int i = 1; i <= n; ++i) {
ans = max(ans, a[i].st-a[i-1].st + c[i] - b[i-1]);
}
cout << ans << '\n';
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(NULL);
int t = 1;
// cin >> t;
while (t--) {
solve();
}
return 0;
}
/*
*/
