#include <bits/stdc++.h>
using namespace std;
#define yasuho ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
typedef long long ll;
const ll MOD = 1e9+7;
void solve(){
ll n; cin >> n;
vector<pair<ll, ll>> v(n+1);
for(int i=1; i<=n; i++) cin >> v[i].first >> v[i].second;
sort(v.begin()+1, v.end());
vector<ll> prefix(n+2, 0), suffix(n+2, 0);
for(int i=n; i>=1; i--){
suffix[i] = v[i].second + suffix[i+1];
}
for(int i=1; i<=n; i++){
prefix[i] = max(prefix[i-1], suffix[i]+v[i].first);
}
ll ans = 0;
for(int i=1; i<=n; i++){
ans = max(ans, prefix[i]-suffix[i+1]-v[i].first);
}
cout << ans << endl;
return;
}
int main(){
yasuho // remove for interactive problem
ll t;
t = 1;
//cin >> t;
while(t--) solve();
}
