#include <bits/stdc++.h>
using namespace std;
const int maxn = 5e5+10;
long long tree[1<<20], lazy[1<<20];
void flush(int node, int l, int r){
if(!lazy[node]) return;
tree[node] += lazy[node];
if(l!=r){
lazy[2*node] += lazy[node];
lazy[2*node+1] += lazy[node];
}
lazy[node] = 0;
}
void update(int node, int tl, int tr, int l, int r, long long v){
flush(node, tl, tr);
if(tl > r or tr < l) return;
if(tl >= l and tr <= r){
lazy[node] += v;
flush(node, tl, tr);
return;
}
int mid = (tl + tr) >> 1;
update(2*node, tl, mid, l, r, v);
update(2*node+1, mid+1, tr, l, r, v);
tree[node] = max(tree[2*node], tree[2*node+1]);
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
int n;
cin >> n;
vector<array<long long, 2>> v(n);
for(int i=0; i<n; i++) cin >> v[i][0] >> v[i][1];
sort(v.begin(), v.end());
long long ans = 0;
for(int i=0; i<n; i++){
update(1, 1, n, 1, i+1, v[i][1]);
update(1, 1, n, i+1, i+1, v[i][0]);
ans = max(ans, tree[1] - v[i][0]);
}
cout << ans << "\n";
return 0;
}
