#include <bits/stdc++.h>
using namespace std;
#define si(a) (long)a.size()
#define fi first
#define se second
#define all(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(int)(n);++i)
template<typename S,typename F>bool chmin(S&a,F b){return b<a?(a=b,1):0;}
template<typename S,typename F>bool chmax(S&a,F b){return b>a?(a=b,1):0;}
bool _=(ios::sync_with_stdio(0),cin.tie(0),cout<<fixed<<setprecision(16),0);


int main(){
    int N,L,K;
    cin>>N>>L>>K;
    vector<int> A(N+2);
    rep(i,N)cin>>A[i+1];
    A[0]=0;
    A[N+1]=L;
    int ok=0;
    int ng=1e9+10;
    while(ng-ok>1){
        int m=(ok+ng)/2;
        vector<int> L(N);
        {
            int l=0;
            int mi=1e9;
            for(int r=1;r<=N;r++){
                L[r-1]=mi;
                while(A[r]-A[l+1]>=m)l++;
                if(A[r]-A[l]>=m){
                    chmin(mi, r-l+(l==0));
                    chmin(L[r-1], r-l+(l==0)+1);
                }
            }
        }
        vector<int> R(N);
        {
            int r=N+1;
            int mi=1e9;
            for(int l=N;l>=1;l--){
                R[l-1]=mi;
                while(A[r-1]-A[l]>=m)r--;
                if(A[r]-A[l]>=m){
                    chmin(mi,r-l+(r==N-1));
                    chmin(R[l-1], r-l+(r==N-1)+1);
                }
            }
        }
        // rep(i,N){
        //     if(m==5){
        //         cout<<L[i]<<" "<<R[i]<<"\n";
        //     }
        // }
        bool f=0;
        rep(i,N)if(L[i]+R[i]<=N-K+5)f=1;
        if(f)ok=m;
        else ng=m;
    }
    cout<<ok<<"\n";
}