#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
int n;
cin >> n;
pair<int,int> arr[n];
for (int i = 0; i<n; i++){
int a,b;
cin >> a >> b;
arr[i] = {a,b};
}
sort(arr,arr+n);
vector<int> pf(n+1, 0);
vector<int> sf(n, 0);
for (int i = 1; i<=n; i++){
pf[i] = pf[i-1] + arr[i-1].second;
}
for (int i = 0; i<n; i++){
sf[i] = pf[i+1] - arr[i].first;
}
for (int i = n-2; i>=0; i--){
sf[i] = max(sf[i], sf[i+1]);
}
int ans = 0;
for (int i = 0; i<n; i++){
int one = arr[i].first - pf[i];
int two = sf[i];
ans = max(ans, one+two);
}
cout << ans;
return 0;
}
