#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define sz(v) (int)v.size()
#define MOO(i, a, b) for(int i=a; i<b; i++)
#define M00(i, a) for(int i=0; i<a; i++)
#define MOOd(i,a,b) for(int i = (b)-1; i >= a; i--)
#define M00d(i,a) for(int i = (a)-1; i>=0; i--)
#define FAST ios::sync_with_stdio(0); cin.tie(0);
#define finish(x) return cout << x << '\n', 0;
#define dbg(x) cerr << ">>> " << #x << " = " << x << "\n";
#define _ << " _ " <<
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int,int> pi;
typedef pair<ld,ld> pd;
typedef complex<ld> cd;
int main() { FAST
int n; cin >> n;
vector<pair<ll,ll>> arr(n);
M00(i, n) cin >> arr[i].f >> arr[i].s;
sort(all(arr));
vector<ll> v;
M00(i, n) {
v.pb(arr[i].s);
if(i != n-1) v.pb(arr[i].f-arr[i+1].f);
}
ll mx = 0;
ll cur = 0;
M00(i, sz(v)) {
cur = max(cur+v[i], v[i]);
mx = max(mx, cur);
}
finish(mx);
}
