#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,p,r;
vector<int>a;
int dp[2002][2002];
bool oke(int jrk){
for(int q=1;q<=n;q++){
int bsr=upper_bound(a.begin()+1,a.end(),a[q]-2*jrk)-a.begin()-1;
int kcl=upper_bound(a.begin()+1,a.end(),a[q]-jrk)-a.begin()-1;
for(int w=0;w<=r;w++){
dp[q][w]=1e18;
if(w>=1){
dp[q][w]=min(dp[q][w-1],dp[bsr][w-1]);
}
dp[q][w]=min(dp[q][w],dp[kcl][w]+1);
}
}
//if(jrk==3)cout<<dp[n][r]<<"K"<<endl;
return dp[n][r]<=p;
}
signed main(){
cin>>n>>p>>r;
for(int q=1;q<=n;q++){
int x; cin>>x;
a.push_back(x);
}
if(p+r>=n){
cout<<1<<endl;
return 0;
}
a.push_back(0);
sort(a.begin(),a.end());
int l=1,r=1e9;
int ans=-1;
while(l<=r){
int mid=(l+r)/2;
if(oke(mid)){
ans=mid;
r=mid-1;
}
else{
l=mid+1;
}
}
cout<<ans<<endl;
}
