#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
struct st{
ll a,b;
};
#define MAXN 500005
const ll INF = 1e18;
st all[MAXN];
map <ll,int> mp;
int hsh = 0;
bool cmp(st x,st y)
{
return x.a < y.a;
}
ll tree[4*MAXN];
ll lazy[4*MAXN];
void push(int node,int left,int right)
{
if(lazy[node]!=0)
{
tree[node] += lazy[node];
if(left != right)
{
lazy[node*2] += lazy[node];
lazy[node*2+1] += lazy[node];
}
lazy[node] = 0;
}
}
void update(int node,int left,int right,int l,int r,ll val)
{
push(node,left,right);
if(left > right || left > r || l > right)return ;
if(left >= l && right <= r)
{
lazy[node]+=val;
push(node,left,right);
return ;
}
int mid = left+right>>1;
update(node*2,left,mid,l,r,val);
update(node*2+1,mid+1,right,l,r,val);
tree[node]=max(tree[node*2],tree[node*2+1]);
}
ll query(int node,int left,int right,int l,int r)
{
push(node,left,right);
if(left > right || left > r || l > right)return -INF;
if(left >= l && right <= r)return tree[node];
int mid = left+right>>1;
return max(query(node*2,left,mid,l,r),query(node*2+1,mid+1,right,l,r));
}
void build(int node,int left,int right)
{
if(left == right)
{
tree[node]=-INF;
return ;
}
int mid=left+right>>1;
build(node*2,left,mid);
build(node*2+1,mid+1,right);
tree[node]=-INF;
}
int main()
{
ios_base::sync_with_stdio(false);
int n;
cin >> n;
for(int i = 0; i < n; i++)
{
ll a,b;
cin >> a >> b;
st ss;
ss.a=a;ss.b=b;
all[i]=ss;
}
sort(all,all+n,cmp);
build(1,1,n);
ll ans = -INF;
for(int i = 0; i < n; i++)
{
ll a = all[i].a;
ll b = all[i].b;
if(!mp[a])mp[a]=++hsh;
int code = mp[a];
if(query(1,1,n,code,code) == -INF)update(1,1,n,code,code,INF+a);
update(1,1,n,1,code,b);
ans = max(ans,query(1,1,n,1,n)-a);
}
cout << ans;
return 0;
}
