#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <numeric>
#include <string>
#include <bitset>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <random>
#include <ctime>
#include <chrono>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)((x).size())
typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
//typedef __int128_t int128;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const char en = '\n';
const int INF = 1e9 + 7;
const ll INFLL = 1e18;
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
#ifdef __APPLE__
#include "debug.h"
//#define debug(...) 42
#else
#define debug(...) 42
#endif
void solve() {
int n;
cin >> n;
vector<pll> a(n);
for (int i = 0; i < n; ++i) {
cin >> a[i].first >> a[i].second;
}
sort(all(a));
ll ans = a[0].second;
ll prev = a[0].second, now = 0;
for (int i = 1; i < n; ++i) {
now = a[i].second;
now += max(0LL, prev + a[i - 1].first - a[i].first);
ans = max(ans, now);
prev = now;
}
cout << ans << en;
}
void stupid() {
int n;
cin >> n;
vector<pll> a(n);
ll ans = 0;
for (int i = 0; i < n; ++i) {
cin >> a[i].first >> a[i].second;
ans = max(ans, a[i].second);
}
sort(all(a));
for (int i = 0; i < n; ++i) {
ll now = a[i].first + a[i].second;
for (int j = i + 1; j < n; ++j) {
now += a[j].second;
now -= a[j].first;
ans = max(ans, now);
now += a[j].first;
}
}
cout << ans << en;
}
int main() {
#ifdef __APPLE__
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0);
cin.tie(0);
#endif
solve();
// stupid();
return 0;
}
