#include<bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
const ll MOD=1e9+7;
const ll MOD2=998244353;
const ll N=1e6+5;
const ld pi=acos(-1);
const ll INF=(1LL<<60);
#define SQ(i) ((i)*(i))
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define setp setprecision
#define lwb lower_bound
#define SZ(_a) (ll)_a.size()
ll n,JOI,t,x[N],u[N];
bool ck(ll k){
REP1(i,n)x[i]=u[i]-2*k*t*i;
ll gl=1,gr=n;
for(int i=1;i<=JOI;i++)gl=(x[i]>x[gl]?i:gl);
for(int i=JOI;i<=n;i++)gr=(x[i]<x[gr]?i:gr);
ll ql=JOI,qr=JOI;
ll lv=x[ql],rv=x[qr];
while(ql>=gl||qr<=gr){
ll bl=ql,br=qr;
for(;qr<=gr&&lv>=x[qr];qr++)rv=min(rv,x[qr]);
for(;ql>=gl&&x[ql]>=rv;ql--)lv=max(lv,x[ql]);
if(bl==ql&&br==qr)return 0;
}
ql=1;qr=n;
lv=x[ql];rv=x[qr];
while(ql<=gl||qr>=gr){
ll bl=ql,br=qr;
for(;qr>=gr&&lv>=x[qr];qr--)rv=min(rv,x[qr]);
for(;ql<=gl&&x[ql]>=rv;ql++)lv=max(lv,x[ql]);
if(bl==ql&&br==qr)return 0;
}
return 1;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>JOI>>t;
REP1(i,n)cin>>u[i];
ll l=-1,r=1e9+10;
while(r-l>1){
ll mid=(l+r)>>1;
if(ck(mid)){
r=mid;
}else{
l=mid;
}
}
cout<<r<<"\n";
return 0;
}
