/*
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
*/
// lethal option
#include<bits/stdc++.h>
using namespace std;
#define all(flg) flg.begin(), flg.end()
#define int long long
#define pb push_back
#define fi first
#define se second
#define endl "\n"
#define eb emplace_back
#define ii pair<int, int>
#define vi vector<int>
#define PI 3.141592653589793238462643383279502884
#define ll long long
#define ld long double
#define for1(i, ff, gg) for(int i = ff; i <= gg; ++i)
#define for2(i, ff, gg) for(int i = ff; i >= gg; --i)
const ll mod = 1e9 + 7;
const int maxN = 300005;
const ll oo = 1e18 + 7;
int n, a[maxN];
int x, y, z, k;
int ans = 0;
vector<ii> ed;
signed main(){
// freopen(".inp", "r", stdin);
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
z = 0;
cin >> n;
for1(i, 1, n){
int sz, vl; cin >> sz >> vl;
ed.pb(ii(sz, vl));
}
sort(all(ed));
for(ii pr : ed){
int sz = pr.fi;
int vl = pr.se;
ans = max(ans, vl - sz + z);
z = max(z + vl, vl + sz);
}
cout << ans << endl;
}
