#include<bits/stdc++.h>
#define fi first
#define se second
using namespace std;
typedef long long ll;
int n;
pair<ll, int> v[500002];
ll sp[500002], mxx[500002];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
for(int i = 1; i <= n; ++i)
cin >> v[i].fi >> v[i].se;
sort(v + 1, v + n + 1);
for(int i = 1; i <= n; ++i)
{
sp[i] = sp[i-1] + v[i-1].fi + v[i].se - v[i].fi;
// cout << sp[i] << " ";
}
// cout << '\n';
mxx[n] = sp[n];
for(int i = n-1; i >= 1; --i)
mxx[i] = max(mxx[i+1], sp[i]);
ll ans = 0;
for(int i = 1; i <= n; ++i)
{
// cout << mxx[i] + v[i].fi << " " << - sp[i-1] - v[i-1].fi << '\n';
ans = max(ans, mxx[i] + v[i].fi - sp[i-1] - v[i-1].fi);
}
cout << ans;
return 0;
}
