#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> indexed_multiset;
#define int long long
#define double long double
#define pb push_back
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define debug(x) cout << #x << " = " << x << '\n';
#define vdebug(a) cout << #a << " = "; for(auto x : a) cout << x << " "; cout << '\n';
const double eps = 1e-9;
const int mod = 1e9 + 7;
const int N = 2e5 + 5;
const int INF = 1e18;
signed main(){
fastio;
int n;
cin >> n;
vector<pair<int, int>> v(n);
vector<int> pref1(n);
vector<int> pref2(n);
for(int i = 0; i < n; i++){
cin >> v[i].first >> v[i].second;
}
sort(v.begin(), v.end());
for(int i = 0; i < n; i++){
if(i == 0){
pref1[i] = 0;
pref2[i] = v[i].second;
}else{
pref1[i] = pref1[i - 1] + v[i].first - v[i - 1].first;
pref2[i] = pref2[i - 1] + v[i].second;
}
}
int ans = 0;
for(int i = 0; i < n; i++){
ans = max(ans, pref2[i] - pref1[i]);
}
cout << ans << '\n';
}
/*
freopen("x.in", "r", stdin);
freopen("x.out", "w", stdout);
*/
//atilla
