#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 5e5 + 7;
int n;
ll pre[mxN], mx[mxN];
ii a[mxN];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//freopen(task".INP", "r", stdin);
//freopen(task".OUT", "w", stdout);
cin >> n;
for (int i = 1; i <= n; i++)
cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; i++)
pre[i] = pre[i - 1] + a[i].se;
ll ans = 0;
for (int i = n; i >= 1; i--)
{
mx[i] = max(mx[i + 1], pre[i] - a[i].fi);
ans = max(ans, mx[i] - pre[i - 1] + a[i].fi);
}
cout << ans << endl;
}
