//fast
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(n) for(int i = 0 ; i<n ; i++)
#define all(x) x.begin(),x.end()
#define pb push_back
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
pair<ll,ll> tab[n];
rep(n){
cin >> tab[i].first >> tab[i].second;
}
sort(tab,tab+n);
ll w = tab[0].second;
ll maks = 0;
maks = tab[0].first;
ll sum = tab[0].second;
for (int i = 1 ; i<n ; i++){
maks = max(maks,tab[i].first-sum);
sum+=tab[i].second;
w = max(maks+sum-tab[i].first,w);
}
cout << w << '\n';
}
