#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
#define xdd cout<<"HAHA"<<endl;
#define bug1(xd) cout<<xd<<endl;
#define bug2(xd,xd1) cout<<xd<<" "<<xd1<<endl;
#define bug3(xd,xd1,xd2) cout<<xd<<" "<<xd1<<" "<<xd2<<endl;
#define bug4(xd,xd1,xd2,xd3) cout<<xd<<" "<<xd1<<" "<<xd2<<" "<<xd3<<endl;
#define bug5(xd,xd1,xd2,xd3,xd4) cout<<xd<<" "<<xd1<<" "<<xd2<<" "<<xd3<<" "<<xd4<<endl;
#define bug6(xd,xd1,xd2,xd3,xd4,xd5) cout<<xd<<" "<<xd1<<" "<<xd2<<" "<<xd3<<" "<<xd4<<" "<<xd5<<endl;
#define bug7(xd,xd1,xd2,xd3,xd4,xd5,xd6) cout<<xd<<" "<<xd1<<" "<<xd2<<" "<<xd3<<" "<<xd4<<" "<<xd5<<" "<<xd6<<endl;
const int mn=5e5+5;
const int mod=1e9+7;
vector<pii> v,cp;
int p[mn];
signed main(){
//freopen("","r",stdin);
//freopen("","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin>>n;
for (int i=1;i<=n;i++){
int a,b;
cin>>a>>b;
v.pb({a,b});
}
sort(v.begin(),v.end());
int i=0;
cp.pb({0,0});
while (i<v.size()){
int st=v[i].fi;
int sum=0;
while (i!=v.size()&&v[i].fi==st) sum+=v[i++].se;
cp.pb({st,sum});
}
int mx=LLONG_MIN;
int ans=0;
for (int i=1;i<cp.size();i++){
p[i]=p[i-1]+cp[i].se;
mx=max(mx,cp[i].fi-p[i-1]);
ans=max(ans,p[i]-cp[i].fi+mx);
}
cout<<ans;
}
