#pragma GCC optimize("O3")
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
tree<int,int,greater<int>,rb_tree_tag,tree_order_statistics_node_update> map_t;
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for(int i = 0; i < (a); ++i)
#define sz(x) (int)x.size()
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
#define REV(x) reverse(x.begin(),x.end())
int dx[]={-1,0,1,0};
int dy[]={0,-1,0,1};
const int mxN=5e5+5;
const ll INF=1e17;
pair<ll,int> arr[mxN];
ll pref[mxN];
int n;
ll t[4*mxN];
void build(int v,int tl,int tr) {
if(tl==tr) {
t[v]=pref[tl];
return;
}
int mid=tl+(tr-tl)/2;
build(2*v,tl,mid);
build(2*v+1,mid+1,tr);
t[v]=max(t[2*v],t[2*v+1]);
}
ll qry(int v,int tl,int tr,int l,int r) {
if(tl>r || tr<l)
return -INF;
if(tl>=l && tr<=r)
return t[v];
int mid=tl+(tr-tl)/2;
return max(qry(2*v,tl,mid,l,r),qry(2*v+1,mid+1,tr,l,r));
}
int main() {
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
F0R(i,n)
cin >> arr[i].first >> arr[i].second;
sort(arr,arr+n);
pref[0]=arr[0].second;
FOR(i,1,n)
pref[i]=pref[i-1]+arr[i].second;
F0R(i,n)
pref[i]-=arr[i].first;
build(1,0,n-1);
ll best=-INF;
F0R(i,n) {
ll val=qry(1,0,n-1,i,n-1);
ll bef=0;
if(i!=0)
bef=pref[i-1]+arr[i-1].first;
best=max(best,val+arr[i].first-bef);
}
cout << best;
return 0;
}
