#include <bits/stdc++.h>
using namespace std;
#define int ll
#define MAX LLONG_MAX
#define st first
#define nd second
#define endl '\n'
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(), x.end()
typedef long long ll;
typedef pair< int, int > ii;
typedef pair< int, ii > iii;
typedef vector< int > vi;
typedef vector< ii > vii;
typedef vector< iii > viii;
typedef vector< vi > vvi;
typedef vector< vii > vvii;
typedef vector< viii > vviii;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n; cin >> n;
ii a[n];
for(int i=0; i<n; i++) cin >> a[i].st >> a[i].nd;
sort(a, a+n);
int ans = LLONG_MIN, base = LLONG_MIN;
for(int i=0; i<n; i++){
base = max(base, a[i].st) + a[i].nd;
ans = max(ans, base - a[i].st);
ans = max(ans, a[i].nd);
}
cout << ans;
}
