#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
//using namespace __gnu_pbds;
#define speed ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define russian setlocale(LC_ALL,"Russian_Russia.20866");
#define file freopen("onlyone.in", "r", stdin), freopen("onlyone.out", "w", stdout);
#define ll long long
#define ull unsigned long long
#define ld long double
#define pll pair<ll, ll>
#define pii pair<int, int>
#define all(s) s.begin(), s.end()
#define pb push_back
#define ins insert
#define mp make_pair
#define sz(x) x.size()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define mem(x) memset(x, 0, sizeof(x))
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll N = 500010;
const ll M = 600000;
const ll block = 316;
const ll mod = 1e9 + 7;
const ll P = 263;
const ld pi = acos(-1);
const ll inf = 1e9;
ll add(ll a, ll b) {
if(a + b < 0) return a + b + mod;
if(a + b >= mod) return a + b - mod;
return a + b;
}
ll sub(ll a, ll b) {
return (a - b + mod) % mod;
}
ll mul(ll a, ll b) {
return a * 1LL * b % mod;
}
ll binpow(ll a, ll n) {
ll res = 1;
while(n) {
if (n & 1) res = mul(res, a);
a = mul(a, a);
n >>= 1;
}
return res;
}
ll inv(ll x) {
return binpow(x, mod - 2);
}
ll n;
pair<ll, ll> a[N];
ll dp[N];
void solve() {
cin >> n;
for(ll i = 1; i <= n; i++) {
cin >> a[i].F >> a[i].S;
}
sort(a + 1, a + n + 1);
dp[0] = 0LL;
ll ans = 0LL;
for(ll i = 1; i <= n; i++) {
dp[i] = max(dp[i - 1] + a[i].S, a[i].F + a[i].S);//min
ans = max(ans, dp[i] - a[i].F);//max
}
cout << ans << '\n';
}
signed main() {
speed;
//file
int test = 1;
//cin >> test;
while(test--) {
solve();
}
}
