#include<bits/stdc++.h>
#define ll long long
#define faster ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define sp << " "
#define task "tl"
using namespace std;
pair<ll,ll> a[500005];
ll mcd[500005];
ll n;
void sub123(){
sort(a+1,a+n+1);
for(ll i = 1; i <= n; i++) mcd[i]=mcd[i-1]+a[i].second;
ll ma = -1e18;
for(ll i = 1; i <= n; i++){
for(ll j = i; j <= n; j++){
ma = max(ma, (mcd[j]-a[j].first)-(mcd[i-1]-a[i].first));
}
}
cout << ma;
}
void sub4(){
sort(a+1,a+n+1);
for(ll i = 1; i <= n; i++) mcd[i]=mcd[i-1]+a[i].second;
ll ma = -1e18, mi = 1e18;
for(ll i = 1; i <= n; i++){
mi = min(mi, mcd[i-1]-a[i].first);
ma = max(ma, mcd[i]-a[i].first-mi);
}
cout << ma;
}
int main(){
faster;
cin >> n;
for(ll i = 1; i <= n; i++){
cin >> a[i].first >> a[i].second;
}
if(n<=5000){
sub123();
}
else{
sub4();
}
return 0;
}
