#include<bits/stdc++.h>
typedef long long ll;
#define pb push_back
#define fr first
#define sc second
#define endl '\n'
using namespace std;
#define mid ((left+right)>>1)
const ll inf=2e18;
int n,k;
ll t;
ll arr[100023];
int m;
ll mn[100023][17],mx[100023][17];
bool f(ll s){
s*=2*t;
ll d=0;
for(int i=k+1;i<=n;i++){
d+=s-(arr[i]-arr[i-1]);
mx[i-k][0]=mn[i-k][0]=d;
}
m=n-k;
for(int j=1;j<17;j++){
for(int i=0;i<=m;i++){
if(i+(1<<(j-1))>m)mn[i][j]=mn[i][j-1];
else mn[i][j]=min(mn[i][j-1],mn[i+(1<<(j-1))][j-1]);
if(i+(1<<(j-1))>m)mx[i][j]=mx[i][j-1];
else mx[i][j]=max(mx[i][j-1],mx[i+(1<<(j-1))][j-1]);
}
}
d=0;
int l=0,r=0;
for(int i=k;i>=1;i--){
for(int j=17-1;j>=0;j--){
if(mx[l][j]+d<0){
l+=(1<<j);
l=min(l,m+1);
if(l==m+1)return false;
}
if(r-(1<<j)+1>=0&&mx[r-(1<<j)+1][j]+d<0){
r-=(1<<j);
if(r==-1)return false;
}
}
if(l>r)return false;
for(int j=17-1;j>=0;j--){
if(r==m+1)break;
if(mn[r][j]+d>=0){
r+=(1<<j);
r=min(r,m+1);
}
}
r--;
d+=s-(arr[i]-arr[i-1]);
}
return r==m;
}
signed main(){
ios_base::sync_with_stdio(23^23);cin.tie(0);
cin>>n>>k>>t;
for(int i=1;i<=n;i++){
cin>>arr[i];
}
int l=0,r=1e9;
while(l<r){
ll s=(l+r)/2;
if(f(s))r=s;
else l=s+1;
}
cout<<l<<endl;
}
