#include <bits/stdc++.h>
using namespace std;
#define sp " "
#define endl "\n";
#define fastio() cin.tie(0), ios_base::sync_with_stdio(0)
#define pb push_back
#define pii pair<int, int>
#define st first
#define nd second
#define N 500005
#define int long long
const int modulo = 1e9 + 7, INF = 2e18 + 7;;
int pre[N], maks[N];
pii arr[N];
int32_t main()
{
fastio();
int n;
cin>>n;
for (int i = 1; i <= n; i++)
cin>>arr[i].st>>arr[i].nd;
sort(arr + 1, arr + 1 + n);
for (int i = 1; i <= n; i++)
pre[i] = pre[i - 1] + arr[i].nd;
maks[n + 1] = -INF;
for (int i = n; i >= 1; i--)
maks[i] = max(maks[i + 1], pre[i] - arr[i].st);
int ans = 0;
for (int i = 1; i <= n; i++)
{
ans = max(ans, maks[i] - pre[i - 1] + arr[i].st);
}
cout<<ans<<endl;
cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " seconds\n";
}
