#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define pll pair<long long, long long>
const int sz = 1e6 + 5;
pll a[sz];
int n;
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen("main.inp","r",stdin);
//freopen("main.out","w",stdout);
cin >> n;
for(int i=1;i<=n;++i){
cin>>a[i].first>>a[i].second;
}
sort(a+1, a+n+1);
// S - (A_max - Amin) <-> S - A_max + A_min
long long ans = 0;
long long best = 0;
for(int i=1;i<=n;++i){
best += a[i].second;
best = max(best, a[i].first + a[i].second); //start with new painting
ans = max(ans, best - a[i].first);
}
cout<<ans;
return 0;
}
