#include <bits/stdc++.h>
using namespace std;
#define ull unsigned long long
#define lll __int128
#define ll long long
const ll mod = 1e9 + 7;
const ll mod1 = 998244353;
const ll naim = 1e9;
const ll max_bit = 60;
const ull tom = ULLONG_MAX;
const ll MAXN = 100005;
const ll LOG = 20;
const ll NAIM = 1e18;
const ll N = 2e6 + 5;
int main() {
#define pb push_back
#define ff first
#define ss second
#define _ << " " <<
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define BlueCrowner ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORD(i, a, b) for (ll i = (a); i >= (b); i--)
// ---------- GCD ----------
auto gcd = [&](ll a, ll b) {
while (b) {
a %= b;
swap(a, b);
}
return a;
};
// ---------- LCM ----------
auto lcm = [&](ll a, ll b) {
return a / gcd(a, b) * b;
};
// ---------- Modular Exponentiation ----------
function<ll(ll, ll, ll)> modpow = [&](ll a, ll b, ll m) {
ll c = 1;
a %= m;
while (b > 0) {
if (b & 1) c = c * a % m;
a = a * a % m;
b >>= 1;
}
return c;
};
// ---------- Modular Inverse (Fermat’s Little Theorem) ----------
function<ll(ll, ll)> modinv = [&](ll a, ll m) {
return modpow(a, m - 2, m);
};
// ---------- Factorials and Inverse Factorials ----------
vector<ll> fact(N), invfact(N);
auto pre_fact = [&](ll n = N-1, ll m = mod) {
fact[0] = 1;
for (ll i = 1; i <= n; i++) fact[i] = fact[i-1] * i % m;
invfact[n] = modinv(fact[n], m);
for (ll i = n; i > 0; i--) invfact[i-1] = invfact[i] * i % m;
};
// ---------- nCr ----------
auto nCr = [&](ll n, ll r, ll m = mod) {
if (r < 0 || r > n) return 0LL;
return fact[n] * invfact[r] % m * invfact[n-r] % m;
};
// ---------- Sieve of Eratosthenes ----------
vector<ll> primes;
vector<bool> is_prime(N);
auto sieve = [&](ll n = N-1) {
fill(is_prime.begin(), is_prime.begin() + n + 1, true);
is_prime[0] = is_prime[1] = false;
for (ll i = 2; i * i <= n; i++) {
if (is_prime[i]) {
for (ll j = i * i; j <= n; j += i)
is_prime[j] = false;
}
}
for (ll i = 2; i <= n; i++)
if (is_prime[i]) primes.pb(i);
};
function<void()> solve = [&]() {
ll n; cin >> n;
map<ll,ll> mp;
FOR(i, 0, n) {
ll x, y; cin >> x >> y;
mp[x] += y;
}
ll m = mp.size();
vector<ll> a;
vector<ll> b;
for (auto x : mp) { a.pb(x.first); b.pb(x.second); }
vector<ll> p(m+1, 0);
FOR(i, 0, m) p[i+1] = p[i] + b[i];
ll ans = -NAIM;
ll mn = NAIM;
FOR(i, 0, m) {
mn = min(mn, p[i] - a[i]);
ll cand = (p[i+1] - a[i]) - mn;
ans = max(ans, cand);
}
cout << ans << '\n';
};
BlueCrowner;
int t = 1; //cin >> t;
while (t--) {
solve();
}
}
