#include <bits/stdc++.h>
#define pb push_back
#define ll long long
#define pii pair<int, int>
#define xx first
#define yy second
using namespace std;
int n;
pair<ll, ll> ex[500010];
ll ress;
///xx-size; yy-value
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n;
for (int i=0; i<n; i++)
{
ll ss, vv; cin>>ss>>vv;
ex[i].xx=ss; ex[i].yy=vv;
}
sort(ex, ex+n);
ll pref=0;
ll maxx=ex[0].xx;
ress=ex[0].yy+maxx-ex[0].xx;
for (int i=0; i<n; i++)
{
pref+=ex[i].yy;
maxx=max(maxx, ex[i].xx-(pref-ex[i].yy));
ll trRess=pref+maxx-ex[i].xx;
ress=max(ress, trRess);
}
cout<<ress;
}
