#include <bits/stdc++.h>
#include <iostream>
using namespace std;
#define int int64_t
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n; cin>>n;
vector<pair<int, int>>v;
for(int i = 0; i<n; ++i){
int a, b; cin>>a>>b;
v.push_back({a, b});
}
sort(v.begin(), v.end());
vector<int>prefix(n);
prefix[0] = v[0].second;
for(int i = 1; i<n; ++i) prefix[i] = prefix[i-1] + v[i].second;
vector<int>ans(n);
for(int i = 1; i<n; ++i){
int cur = prefix[i] - (v[i].first - v[0].first);
ans[i] = cur;
}
vector<int>suffix(n);
suffix[n-1] = ans[n-1];
for(int i = n-2; i>=0; --i){
suffix[i] = max(suffix[i+1], ans[i]);
}
/*
for(auto u: suffix) cout<<u<<" ";
cout<<endl;
*/
int out = suffix[0];
for(int i = 1; i<n-1; ++i){
int diff = (v[i].first - v[0].first) - prefix[i-1];
out = max(out, suffix[i] + diff);
//if(diff > 0) ans += diff;
}
for(int i = 0; i<n; ++i) out = max(out, v[i].second);
cout<<out;
cout<<'\n';
}
