#include <iostream>
#include <vector>
using namespace std;

const int INF = 1<<20;

int N, L, K;
vector<int> F, C, S;

bool ok(int X){
    C.assign(N+1, INF);
    int sum=0;
    int right=0;
    for (int left=0; left<=N; left++) {
        while (right<=N && sum+F[right]<X) {
            sum += F[right++];
        }
        
        if (right==N+1) break;
        C[left]=right-left;
        if (right == left) right++;
        else sum -= F[left];
    }
    S.assign(N+1, INF);
    S[N]=C[N];
    for (int i=N-1;i>=0;i--) S[i]=min(S[i+1], C[i]);
    bool res = false;
    for (int i=0;i<=N;i++){
        if (i+C[i]+1>N) break;
        if (C[i]+S[i+C[i]+1]<=N-K) {
            res = true;
            break;
        }
    }
    return res;    
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>N>>L>>K;
    vector<int> A(N+1);
    for (int i=0;i<N;i++) cin>>A[i];
    A[N]=L;
    F.assign(N+1, 0);
    F[0]=A[0];
    for (int i=1;i<=N;i++) F[i]=A[i]-A[i-1];
    int l = -1, r=L;
    while(l+1<r){
        int m = (l+r)/2;
        if (ok(m)) l=m;
        else r=m;
    }
    cout << l << "\n";
    return 0;
}