#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 1e6 + 5;
const ll inf = 1e18;
ll S[maxn], A[maxn];
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n;
cin>>n;
vector<pair<ll,ll>> a(n);
for (int i=0; i<n; i++) {
cin>>a[i].first>>a[i].second;
}
sort(a.begin(), a.end());
for (int i=0; i<n; i++) {
S[i+1] = S[i]+a[i].second;
A[i+1] = a[i].first;
}
set<ll> st;
ll hi = -inf;
for (int i=1; i<=n; i++) {
ll cur = S[i]-A[i];
st.insert(A[i]-S[i-1]);
cur += *st.rbegin();
hi = max(hi, cur);
}
cout<<hi<<endl;
return 0;
}
