#include <bits/stdc++.h>
using namespace std;
#define pf(a) printf("%.9f", a)
#define SZ size()
#define ll long long
#define pb push_back
#define BBC ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
void W2dNHK() {
ll n;
cin>>n;
ll i;
pair<ll,ll> a[n+1];
for(i=1 ; i<=n ; i++ ){
cin>>a[i].first>>a[i].second;
}
sort(a+1,a+n+1);
ll c,ans;
for(i=1 ; i <=n ; i ++ ){
c+=a[i].second;
c=max(c,a[i].first+a[i].second);
ans=max(ans,c-a[i].first);
}
cout<<ans;
}
int main() {
BBC
ll tc = 1;
//cin >> tc;
while (tc--) {
W2dNHK();
}
}
