#include <bits/stdc++.h>
using namespace std;
const long long INFll = 1e18;
const int INFii = 1e9;
const long long mod = (long long) 1e9 + 7;
typedef long long ll;
typedef int ii;
typedef double dbl;
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define maxn 550000
//LEMBRAR DE MUDAR
ll n, ps[maxn];
pair<ll,ll> a[maxn];
int main() {
ios::sync_with_stdio(false); cin.tie(0);
//freopen("in.in", "r", stdin);
//freopen("____.out", "w", stdout);
cin >> n;
for(ll i = 1; i <= n; i++) {
cin >> a[i].fr >> a[i].sc;
}
sort(a+1,a+1+n);
for(ll i = 1; i <= n; i++)
ps[i] = ps[i-1] + a[i].sc;
ll best = -INFll;
ll ans = 0;
for(ll i = n; i >= 1; i--) {
best = max(best, ps[i] - a[i].fr);
ans = max(ans, best - ps[i-1] + a[i].fr);
}
cout << ans << endl;
return 0;
}
