#include <bits/stdc++.h>
#define int long long
#define fi first
#define sc second
using namespace std;
const int N = 555555;
int n, ans, pf[N], pfm[N];
pair<int, int> a[N];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
for(int i = 1;i<=n;i++){
cin >> a[i].fi >> a[i].sc;
}
sort(a + 1, a + n + 1);
for(int i = 1;i<=n;i++){
pf[i] = pf[i - 1] + a[i].sc;
}
pfm[n] = pf[n] - a[n].fi;
for(int i = n - 1;i>=1;i--){
pfm[i] = max(pfm[i + 1], pf[i] - a[i].fi);
}
for(int i = 1;i<=n;i++){
ans = max(ans, pfm[i] - pf[i - 1] + a[i].fi);
}
cout << ans;
}
