// Author: Teoman Ata Korkmaz
#include <bits/stdc++.h>
#define int int_fast64_t
using namespace std;
///////////////////////////////////////////////////////////
int n,k,b;
vector<int> v;
vector<vector<int>> dp;
inline bool __f(int w){
dp.assign(n+2,vector<int>(b+2,1e9));
dp[0][0]=0;
for(int i=0;i<n;i++){
int it_k=lower_bound(v.begin(),v.end(),v[i]+w)-v.begin();
int it_b=lower_bound(v.begin(),v.end(),v[i]+2*w)-v.begin();
for(int j=0;j<=b;j++){
dp[it_k][j]=min(dp[it_k][j],dp[i][j]+1);
dp[it_b][j+1]=min(dp[it_b][j+1],dp[i][j]);
}
}
/*cerr<<"w:"<<w<<endl;
for(auto t:dp){
cerr<<"dp:";
for(auto i:t)cerr<<i<<",";
cerr<<endl;
}cerr<<endl;*/
for(int j=0;j<=b;j++)if(dp[n][j]<=k)return true;
return false;
}
signed main(void){
cin>>n>>k>>b;
v.resize(n);
for(auto& i:v)cin>>i;
sort(v.begin(),v.end());
v.resize(unique(v.begin(),v.end())-v.begin());
n=v.size();
b=min(n,b);
//cerr<<"v:";for(auto i:v)cerr<<i<<",";cerr<<endl;
int l=1,r=1e9;
while(l<r){
int m=(l+r)>>1;
if(!__f(m))l=m+1;
else r=m;
}
cout<<l<<endl;
}
