#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
constexpr int base = 1<<19;
constexpr int debug = 0;
constexpr ll mini = -1e18-7;
ll tree[2*base+7];
ll tree2[2*base+7];
int p, k;
void push(int v){
tree[2*v] += tree2[v];
tree[2*v+1] += tree2[v];
tree2[2*v] += tree2[v];
tree2[2*v+1] += tree2[v];
tree2[v] = 0;
}
void add(int v, int a, int b, ll val){
if((p > b) || (k < a)){
return;
}
else if((p <= a) && (k >= b)){
tree[v] += val;
tree2[v] += val;
}
else{
int mid = (a+b)/2;
push(v);
add(2*v, a, mid, val); add(2*v+1, mid+1, b, val);
tree[v] = max(tree[2*v], tree[2*v+1]);
}
}
ll query(int v, int a, int b){
ll maksi = mini;
if((p > b) || (k < a)){
return mini;
}
else if((p <= a) && (k >= b)){
return tree[v];
}
else{
int mid = (a+b)/2;
push(v);
maksi = max(query(2*v, a, mid), query(2*v+1, mid+1, b));
tree[v] = max(tree[2*v], tree[2*v+1]);
}
return maksi;
}
vector<pair<ll,ll>> art;
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n; cin >> n;
for(int i = 0; i < n; i++){
pair<ll,ll> a1; cin >> a1.F >> a1.S;
art.pb(a1);
}
sort(art.begin(), art.end());
//fill(tree, tree+2*base+7, mini);
ll best = mini;
for(int i = 0; i < n; i++){
p = 0; k = i;
add(1, 0, base-1, art[i].S);
p = i;
add(1, 0, base-1, art[i].F);
p = 0;
best = max(best, query(1, 0, base-1) - art[i].F);
if(debug){
for(int j = 0; j < n; j++){
p = k = j;
cout << query(1, 0, base-1) << ' ';
}
cout << '\n';
cout << best << '\n';
}
}
cout << best;
return 0;
}
