#include <bits/stdc++.h>
using namespace std;
#define ld long double
#define int long long
#define endl "\n"
const int N = 5e5;
int pref[N + 1];
vector<pair<int,int>> st;
signed main() {
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
int n;
cin>>n;
st.push_back({-1,-1});
for(int i = 0;i < n;i++) {
int a,b;
cin>>a>>b;
st.push_back({a,b});
}
sort(st.begin(),st.end());
for(int i = 1;i <= n;i++) {
pref[i] = pref[i - 1] + st[i].second;
}
// pref[i] - pref[j - 1] - (a[i] - a[j])
// pref[i] - a[i] + a[j] - pref[j - 1];
int mx = 0,res = 0;
for(int i = 1;i <= n;i++) {
mx = max(mx,st[i].first - pref[i - 1]);
res = max(res,pref[i] - st[i].first + mx);
}
cout<<res<<endl;
return 0;
}
