#include<bits/stdc++.h>
#define el '\n'
#define fi first
#define sc second
#define int ll
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;
using ll=long long;
using ull=unsigned long long;
using ld=long double;
const int mod=1e9+7;
const int N=5e5+11;
int n, ans, pre, pfs[N];
pii a[N];
void sol()
{
cin >> n;
for(int i=1;i<=n;i++) cin >> a[i].fi >> a[i].sc;
sort(a+1, a+n+1);
for(int i=1;i<=n;i++) pfs[i]=pfs[i-1]+a[i].sc;
for(int i=1;i<=n;i++)
{
pre=max(pre, a[i].fi-pfs[i-1]);
ans=max(ans, pfs[i]-a[i].fi+pre);
}
cout << ans;
}
signed main()
{
// freopen("divisor.INP", "r", stdin);
// freopen("divisor.OUT", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int t=1;
//cin >> t;
while(t--)
{
sol();
}
}
