// author: khba
// road to IZhO gold
#include <bits/stdc++.h>
using namespace std;
#define int long long
// #ifdef khba
// // #include "save.h"
// #else
// #define print(...) 42
// #endif
void t_main() {
int n, ans = 0; cin >> n;
vector <int> a(n), b(n);
for (int i = 0; i < n; ++i) cin >> a[i] >> b[i];
vector <int> o(n);
iota(begin(o), end(o), 0);
sort(begin(o), end(o), [&] (int r, int l) { return a[r] < a[l]; });
int mx = a[o.front()], s = 0;
for (int i : o) {
mx = max(mx, a[i] - s);
s += b[i];
ans = max(ans, -a[i] + mx + s);
// s - a_max + a_min
// -a_max + pref[max] + a_min - pref[min-1]
}
cout << ans;
}
int32_t main()
{
#ifdef khba
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int32_t t = 1;
// cin >> t;
while (t--) { t_main(); cout << "\n"; }
return 0;
}
