#include <bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
using namespace std;
const int MAXN = 500000;
int n;
pii arr[MAXN+1];
int pre[MAXN+1];
int ans;
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++)
cin >> arr[i].ff >> arr[i].ss;
sort(arr+1, arr+1+n);
int mmax = 0;
for (int i = 1; i <= n; i++) {
pre[i] = pre[i-1] + arr[i].ss;
mmax = max(mmax, arr[i].ff - pre[i-1]);
ans = max(ans, pre[i] - arr[i].ff + mmax);
}
cout << ans << "\n";
}
