#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.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;
#define ll long long
#define str string
#define fastio ios::sync_with_stdio(0), cin.tie(0);
#define fs first
#define ss second
#define endl '\n'
#define all(x) (x).begin(), (x).end()
#define len(x) x.size()
#define print(a) \
for (auto &x : a) \
cout << x << " "; \
cout << endl;
#define printmp(a) \
for (auto &x : a) \
cout << x.fs << " " << x.ss << endl;
const int mod = 1e9 + 7;
const long long INF = LLONG_MAX;
const long long NEG_INF = LLONG_MIN;
void solve()
{
int n;
cin>>n;
vector<pair<ll, ll>> a(n);
for(int i = 0; i < n; i ++)cin>>a[i].fs >> a[i].ss;
sort(all(a), greater<pair<ll, ll>> ());
vector<pair<ll, ll>> b;
int i = 0;
while(i < n){
ll s = a[i].ss;
while(i < n and a[i].fs == a[i + 1].fs)s += a[++ i].ss;
b.push_back({a[i].fs, s});
i ++;
}
b.push_back({b.back().fs, 0});
reverse(all(b));
ll ans = 0, sum = 0;
for(int i = 1; i < (int)b.size(); i ++){
sum = max(b[i].ss, sum + b[i].ss + (b[i - 1].fs - b[i].fs));
ans = max(ans, sum);
}
cout<<ans;
}
signed main()
{
fastio
int t = 1;
// cin >> t;
while (t--)
{
solve();
cout << endl;
}
}
