#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
const ll INF = 1e18;
const ll MOD = 1e9 + 7;
const ll MAXN = 1e6 + 5;
const ll LOG = 30;
#define vll vector <ll>
#define pll pair <ll, ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << " " << (x) << endl;
ll n, m;
pll a [MAXN];
ll pf [MAXN];
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
for(ll i = 1; i <= n; i++){
cin >> a[i].fi >> a[i].se;
}
sort(a+1, a+1+n);
for(ll i = 1; i <= n; i++){
pf[i] = pf[i-1] + a[i].se;
}
ll cnt = 0;
ll ans = 0;
for(ll i = 1; i <= n; i++){
cnt = max(cnt, a[i].fi - pf[i-1]);
ans = max(ans, pf[i]-a[i].fi+cnt);
}
cout << ans << endl;
}
