#include<bits/stdc++.h>
using namespace std;
const int N=5e5+2;
pair<long long, long long> a[N];
int n;
long long node[N*4], lazy[N*4];
void update_lazy(int goc, int l, int r)
{
node[goc]+=lazy[goc];
if(l!=r)
{
lazy[goc*2]+=lazy[goc];
lazy[goc*2+1]+=lazy[goc];
}
lazy[goc]=0;
}
void update_pos(int goc, int l, int r, int pos, long long value)
{
update_lazy(goc, l, r);
if(pos<l or pos>r)return ;
if(l==r)
{
node[goc]+=value;
return;
}
int mid=(l+r)>>1;
update_pos(goc*2, l, mid, pos, value);
update_pos(goc*2+1, mid+1, r, pos, value);
node[goc]=max(node[goc*2], node[goc*2+1]);
}
void update(int goc, int l, int r, int trai, int phai, long long value)
{
update_lazy(goc, l, r);
if(l>phai or r<trai)return;
if(trai<=l and r<=phai)
{
lazy[goc]+=value;
update_lazy(goc, l, r);
return;
}
int mid=(l+r)>>1;
update(goc*2, l, mid, trai, phai, value);
update(goc*2+1, mid+1, r, trai, phai, value);
node[goc]=max(node[goc*2], node[goc*2+1]);
}
long long get(int goc, int l, int r, int trai, int phai)
{
update_lazy(goc, l, r);
if(l>phai or r<trai)return -1e15;
if(trai<=l and r<=phai)return node[goc];
int mid=(l+r)>>1;
return max(get(goc*2, l, mid, trai, phai), get(goc*2+1, mid+1, r, trai, phai));
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
for(int i=1; i<=n; i++)cin>>a[i].first>>a[i].second;
sort(a+1, a+n+1);
long long ans=LLONG_MIN;
for(int i=1; i<=n; i++)
{
update_pos(1, 1, n, i, a[i].first);
update(1, 1, n, 1, i, a[i].second);
ans=max(ans, get(1, 1, n, 1, i)-a[i].first);
}
cout<<ans;
return 0;
}
