// Starcraft 2 enjoyer //
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
#define LSOne(X) ((X) & -(X))
const int N = 5e5 + 5;
const int M = 1e6 + 5;
const int LG = 60;
const int INF = 1e9 + 5;
const int K = 301;
const int B = 150000;
const int MOD = 1e9 + 7;
int n;
pair<long long, long long> paint[N];
long long cur, ans, mn;
inline void solve()
{
cin >> n;
ans = 0;
cur = 0;
for (int x = 0; x < n; x++)
{
cin >> paint[x].first >> paint[x].second;
}
sort(paint, paint + n);
mn = 1e18;
for (int x = 0; x < n; x++)
{
mn = min(mn, -paint[x].first + cur);
cur += paint[x].second;
ans = max(ans, cur - mn - paint[x].first);
// cout << cur << "\n";
}
cout << ans << "\n";
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
for (int x = 1; x <= t; x++)
{
solve();
}
return 0;
}
