#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define endl '\n'
#define INF 1e9+7
#define all(x) x.begin(),x.end()
using namespace std;
using namespace __gnu_pbds;
using ll=long long;
using pii=pair<int,int>;
using ppi=pair<int,pii>;
using oset=tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>;
template<typename T>
void _print(vector<T> x) {cerr<<"{"; for(auto e:x) cerr<<e<<","; cerr<<"}";}
void _print(pii x) {cerr<<"{"<<x.first<<","<<x.second<<"}";}
template<typename T>
void _print(T x) {cerr<<x;}
void dbg() {cerr<<endl;}
template<typename Head,typename... Tail>
void dbg(Head H,Tail... T) {
_print(H);
if(sizeof...(T)) cerr<<",";
else cerr<<"\"]";
dbg(T...);
}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:[\"",dbg(__VA_ARGS__)
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
using pll=pair<ll,ll>;
#define x first
#define y second
const int mxn=5e5+10;
pll ar[mxn];
ll dp[mxn];
int n;
int main () {
ios::sync_with_stdio(false); cin.tie(0);
cin>>n;
for(int i=0;i<n;i++) {
cin>>ar[i].x>>ar[i].y;
//size,value
}
sort(ar,ar+n);
// for(int i=0;i<n;i++) {
// cout<<"{"<<ar[i].x<<","<<ar[i].y<<"}"<<endl;
// }
ll ans=dp[0];
ll mx=ar[0].x;
for(int i=0;i<n;i++) {
if(i) dp[i]=dp[i-1];
dp[i]+=ar[i].y;
// debug(i,ar[i].x,dp[i]);
}
for(int i=1;i<n;i++) {
mx=max(mx,ar[i].x-dp[i-1]);
ans=max(ans,dp[i]-ar[i].x+mx);
// debug(i,mx);
}
cout<<ans<<endl;
}
