#include <bits/stdc++.h>

#define int long long
#define ll long long
#define ld long double
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
int inf=1000000007;
ll infl=1000000000000000007;
int mod=1000000007;
int mod1=998244353;

const int N=100007;

//bool DP[N][N];

int a[N];
int b[N];
int c[N];
int n;

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int k,t;
    cin>>n>>k>>t;
    for(int i=1;i<=n;i++) cin>>a[i];
    int X=k-1,Y=n-k;
    for(int i=1;i<=k-1;i++) b[i]=-(a[k-i+1]-a[k-i]);
    for(int i=1;i<=n-k;i++) c[i]=-(a[k+i]-a[i+k-1]);
    int l=0,r=1000000000,sr,ans=inf; 
    while(l<=r)
    {
        sr=(l+r)/2;
        if(sr*t>1000000000)
        {
            ans=sr;
            r=sr-1;
            continue;
        }
        for(int i=1;i<=X;i++) b[i]+=2*sr*t;
        for(int i=1;i<=Y;i++) c[i]+=2*sr*t;
        
        
        int x=0,y=0,S=0;
        while(true)
        {
			bool is=0;
			int s=0;
			for(int i=x+1;i<=X;i++)
			{
				s+=b[i];
				if(s+S<0) break;
				if(s>0)
				{
					is=1;
					S+=s;
					x=i;
					break;
				}
			}
			s=0;
			for(int i=y+1;i<=Y;i++)
			{
				s+=c[i];
				if(s+S<0) break;
				if(s>0)
				{
					is=1;
					S+=s;
					y=i;
					break;
				}
			}
			if(!is) break;
		}
		int mnx=0,sx=0;
		for(int i=x+1;i<=X;i++) 
		{
			sx+=b[i];
			mnx=min(mnx,sx);
		}
		int mny=0,sy=0;
		for(int i=y+1;i<=Y;i++) 
		{
			sy+=c[i];
			mny=min(mny,sy);
		}
		bool ok=0;
		if(S+mnx>=0&&S+sx+mny>=0) ok=1;
		if(S+mny>=0&&S+sy+mnx>=0) ok=1;
        if(ok)
        {
            ans=sr;
            r=sr-1;
        }
        else l=sr+1;
        for(int i=1;i<=X;i++) b[i]-=2*sr*t;
        for(int i=1;i<=Y;i++) c[i]-=2*sr*t;
    }
    cout<<ans;




    return 0;
}