//tavakol bar khoda
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const int MAXN = (int)5e5 + 7;
const int MOD = (int)1e9 + 7;
const int infint = (int)1e8 + 3;
const ll inf = (ll)1e18;
ll n, part[MAXN];
pair<ll, ll> P[MAXN];
int main()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 0; i < n; i++)
cin >> P[i].first >> P[i].second;
sort(P, P + n);
part[0] = P[0].second;
for (int i = 1; i < n; i++)
part[i] = part[i - 1] + P[i].second;
ll ans = 0, mn = 0;
for (int i = 0; i < n; i++)
{
if(i == 0)
mn = -P[0].first;
else
mn = min(mn, part[i - 1] - P[i].first);
ans = max(ans, part[i] - P[i].first - mn);
}
cout << ans;
}
