#pragma gcc diagnostic "-std=c++1z"
#include <bits/stdc++.h>
using namespace std;
/* /\_/\
(= ._.)
/ > \>
*/
//#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") // codeforces
// #define int long long
#define fi first
#define se second
#define send {ios_base::sync_with_stdio(false);}
#define help {cin.tie(0);}
#define endl '\n'
#define print(x) cout<<(x)<<" ";
#define printl(x) cout<<(x)<<endl
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const int MAXN=5e5+5;
int n;
ll T[4*MAXN],lazy[4*MAXN];
void push(int v) {
if(!lazy[v]) return;
T[2*v] += lazy[v];
lazy[2*v] += lazy[v];
T[2*v+1] += lazy[v];
lazy[2*v+1] += lazy[v];
lazy[v] = 0;
}
ll query(int v,int l,int r,int tl,int tr) {
if(l > r) return 0;
if(l == tl and r == tr) return T[v];
push(v);
int tm = (tl + tr)/2;
return max(query(2*v,l,min(r,tm),tl,tm),query(2*v+1,max(l,tm+1),r,tm+1,tr));
}
void update(int v,int l,int r,int tl,int tr,ll addend) {
if(l > r) return;
if(l == tl and r == tr) {
T[v] += addend;
lazy[v] += addend;
}else {
push(v);
int tm = (tl + tr)/2;
update(2*v,l,min(r,tm),tl,tm,addend);
update(2*v+1,max(l,tm+1),r,tm+1,tr,addend);
T[v] = max(T[2*v],T[2*v+1]);
}
}
signed main(){
send help
cin>>n; pll A[n]; memset(T,0,sizeof(T)); memset(lazy,0,sizeof(lazy));
for(int i=0;i<n;i++) cin>>A[i].fi>>A[i].se;
sort(A,A+n); ll ans = 0;
for(int i=0;i<n;i++) {
update(1,i,i,0,n-1,A[i].fi);
update(1,0,i,0,n-1,A[i].se);
ans = max(ans,query(1,0,i,0,n-1) - A[i].fi);
} printl(ans);
}
