#include <bits/stdc++.h>
using namespace std;
#define vi vector<int>
#define vll vector<long long>
#define pb push_back
using ll= long long;
#define fast_io ios::sync_with_stdio(0); cin.tie(0)
#define inpint(x) int x; cin>>x
#define inpll(x) long long x; cin>>x
#define fl(i, n) for(int i=0; i<n; i++)
#define flo(i, n) for(int i=1; i<=n; i++)
#define int long long
#define pi pair<int, int>
#define mp make_pair
#define ld long double
const int MOD = 7 + (int)1e9;
const int INF = (int)1e18;
//
void solve()
{
int n;
cin>>n;
vector<pi> a(n+1);
for(int i=1; i<=n; i++)
{
cin>>a[i].first>>a[i].second;
}
sort(a.begin()+1, a.end());
vector<int> s(n+1, 0);
for(int i=1; i<=n; i++)
{
s[i] = s[i-1] + a[i].second;
}
int ans = s[1];
//s_i - a_i - (s_(i-1) - a_i);
int mv = -a[1].first;
for(int i=2; i<=n; i++)
{
mv = min(mv, s[i-1] - a[i].first);
int op = s[i] - a[i].first - mv;
ans = max(ans, op);
}
cout<<ans;
}
signed main()
{
fast_io;
int t=1;
//cin>>t;
while(t--)
{
solve();
}
cout<<endl;
}
