#include<iostream>
#include<vector>
#include<algorithm>
#include<climits>
using namespace std;
bool check(const vector<int> &A,int n,int P,int Q,int w){
int ma=min(Q,n);
vector<vector<int>>dp(n+1,vector<int>(ma+1,INT_MAX));
dp[0][0]=0;
for(int i=0;i<n;++i){
for(int q=0;q<=ma;++q){
if(dp[i][q]==INT_MAX)continue;
int cover_until_small=A[i]+w-1;
int j_small=upper_bound(A.begin(),A.end(),cover_until_small)-A.begin();
if(j_small<=n&&dp[j_small][q]>dp[i][q]+1){
dp[j_small][q]=dp[i][q]+1;
}
int cover_until_big=A[i]+2*w-1;
int j_big=upper_bound(A.begin(),A.end(),cover_until_big)-A.begin();
if(q+1<=ma&&j_big<=n&&dp[j_big][q+1]>dp[i][q]){
dp[j_big][q+1]=dp[i][q];
}
}
}
for(int q=0;q<=ma;++q){
if(dp[n][q]<=P)return true;
}
return false;
}
int main(){
int n,P,Q;
cin>>n>>P>>Q;
vector<int>A(n);
for(int i=0;i<n;++i){
cin>>A[i];
}
if(n==0){
cout<<0<<endl;
return 0;
}
sort(A.begin(),A.end());
int low=1;
int high=A[n-1]-A[0]+1;
int ans=high;
while(low<=high){
int mid=(low+high)/2;
if(check(A,n,P,Q,mid)){
ans=mid;
high=mid-1;
}
else{
low=mid+1;
}
}
cout<<ans<<endl;
return 0;
}
