#include<bits/stdc++.h>
#define endl "\n"
using namespace std ;
typedef long long ll;
typedef long double ld ;
#define pb push_back
#define pp pop_back
const int N=1e6+9;
const ll inf=1e18 ;
const ll mod = 1e9+9 ;
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
ll n ,a[N] , x, y,k,t[N],pre[N];
vector<ll>vec;
void solve(){
cin>>n;
vector<pair<ll,ll>>vec(n);
for(int i=0;i<n;i++){
cin>>vec[i].first>>vec[i].second;
}
sort(vec.begin(),vec.end());
pre[0]=vec[0].second;
for(int i=1;i<n;i++){
pre[i]=pre[i-1]+vec[i].second;
}
ll ans=-10,mx=-10;
for(int i=0;i<n;i++){
ll temp=vec[i].first;
if(i>0){
ans=max(pre[i]-temp+mx,ans);
}
ll prel=((i==0)?0:pre[i-1]);
mx=max(mx,temp-prel);
}
cout<<ans;
}
int main(){
fast;
ll t=1;//cin>>t;
while(t--)solve();
return 0;
}
