#include <bits/stdc++.h>
using namespace std;
inline void setup()
{
#ifndef ONLINE_JUDGE
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int n;
long long pre[500001], premin[500001], res = 0;
pair<long long, long long> p[500001];
int main()
{
// setup();
cin >> n;
for (int i = 1; i <= n; ++i)
{
cin >> p[i].first >> p[i].second;
}
sort(p + 1, p + n + 1);
for (int i = 1; i <= n; ++i)
{
premin[i] = min(premin[i - 1], pre[i - 1] - p[i].first);
pre[i] = pre[i - 1] + p[i].second;
res = max(res, pre[i] - p[i].first - premin[i]);
}
cout << res;
return 0;
}
