#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> pi;
#define f first
#define s second
#define FAST ios_base::sync_with_stdio(0); cin.tie(0);
const int maxn = 500010;
const int INF = LLONG_MAX/4;
int n;
vector <pi> v;
int pp[maxn];
int32_t main() {
FAST
cin >> n;
for (int i =0;i<n;i++) {
int a,b; cin >> a >> b;
v.push_back(pi(a,b)); //size, value
}
sort(v.begin(),v.end());
int best = v[0].f;
int ans = 0;
for (int i =0;i<(int)v.size();i++) {
pp[i] = (i == 0 ? 0 : pp[i-1]);
pp[i] += v[i].s;
if (i != 0) best = max(best, v[i].f - pp[i-1]);
ans = max(ans, pp[i] - v[i].f + best);
}
cout << ans;
}
