#include<bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define all(v) (v).begin(),(v).end()
#define F first
#define S second
#define pb push_back
#define popb pop_back
#define ss sort
#define rr reverse
#define pii pair <int, int>
#define pll pair <ll, ll>
using namespace std;
using ld = long double;
using ll = long long;
const int N = 5e5+10;
const ll inf = 1e18;
const int Mod = 1e9+7;
const int P = 273;
int n;
ll a[N], b[N], t[N*4], pref[N];
vector <ll> vec;
void build(int v = 1, int tl = 1, int tr = n)
{
if (tl == tr)
{
t[v] = pref[tl] - vec[tl-1];
return;
}
int tm = tl + tr >> 1;
build(v + v, tl, tm);
build(v + v + 1, tm + 1, tr);
t[v] = max(t[v + v], t[v + v + 1]);
}
ll get(int l, int r, int v = 1, int tl = 1, int tr = n)
{
if (tl > r || tr < l) return -inf;
if (l <= tl && tr <= r) return t[v];
int tm = tl + tr >> 1;
return max(get(l, r, v + v, tl, tm), get(l, r, v + v + 1, tm + 1, tr));
}
void Erali_is_the_best(int testCase)
{
cin >> n;
map <ll, ll> mp;
for (int i = 1; i <= n; ++i)
{
cin >> a[i] >> b[i];
if (!mp.count(a[i])) vec.pb(a[i]);
mp[a[i]] += b[i];
}
ss(all(vec));
vec.resize(unique(all(vec)) - vec.begin());
n = vec.sz();
for (int i = 1; i <= n; ++i)
{
pref[i] = pref[i-1] + mp[vec[i-1]];
}
build();
ll ans = 0, sum = 0;
for (int i = 1; i <= n; ++i)
{
ll val = get(i, n) - sum;
ans = max(vec[i-1] + val, ans);
sum += mp[vec[i-1]];
// cout << ans << " ";
}
cout << ans << "\n";
}
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("cardgame.in","r",stdin);
// freopen("cardgame.out","w",stdout);
int tt = 1;
// cin >> tt;
for (int test = 1; test <= tt; ++test)
{
Erali_is_the_best(test);
}
}
