#include<bits/stdc++.h>
using namespace std;
#define f first
#define s second
typedef long long ll;
typedef long double ld;
typedef pair<int, pair<int, int>> ft;
const ld PI = acos(-1);
const int maxn = 5e5+5;
const int blsz = 1000;
const ll inf = 1e18;
const int mod = 998244353;
int n, m, q;
ll ans = 0, mx = -inf;
pair<ll, ll> A[maxn];
signed main(){
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n;
for(int i = 1; i <= n; i++)cin >> A[i].f >> A[i].s;
sort(A+1, A+n+1);
for(int i = 1; i <= n; i++){
mx = max(mx, A[i].f - A[i-1].s);
A[i].s += A[i-1].s;
ans = max(ans, A[i].s - A[i].f + mx);
}
cout << ans;
}
