#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
#define pii pair<ll, ll>
#define oo 1e18
#define all(v) v.begin(), v.end()
int n;
const int MAX = 5e5 + 5;
pii arr[MAX];
int pre[MAX];
int tree[4 * MAX];
void build(int node, int l, int r){
if(l == r){
tree[node] = pre[l] - arr[l].first;
return;
}
int mid = (l + r) / 2;
build(2 * node, l, mid);
build(2 * node + 1, mid + 1, r);
tree[node] = max(tree[2 * node], tree[2 * node + 1]);
}
int ask(int node, int l, int r, int ql, int qr){
if(qr < l | r < ql) return -oo;
if(ql <= l && r <= qr) return tree[node];
int mid = (l + r) / 2;
return max(ask(2 * node, l, mid, ql, qr), ask(2 * node + 1, mid + 1, r, ql, qr));
}
signed main(){
fill(tree, tree + 4 * MAX, -oo);
cin >> n;
for(int i = 1; i <= n; i++) cin >> arr[i].first >> arr[i].second;
sort(arr + 1, arr + n + 1);
for(int i = 1; i <= n; i++){
pre[i] = pre[i - 1] + arr[i].second;
}
build(1, 1, n);
int upd = 0;
int ans = 0;
for(int i = 1; i <= n; i++){
ans = max(ans, ask(1, 1, n, i, n) + upd + arr[i].first);
upd -= arr[i].second;
}
cout << ans << '\n';
}
