#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#include <ext/rope>
using namespace __gnu_cxx;
typedef tree<long long, null_type, less<long long>,
rb_tree_tag, tree_order_statistics_node_update> pbds;
//less_equal for identical elements
#define DEBUG
#ifdef DEBUG
#define debug(...) printf(__VA_ARGS__);
#else
#define debug(...)
#endif
#define sf scanf
#define pf printf
#define fi first
#define se second
#define pb emplace_back
#define sz(x) (int)x.size()
#define mnto(x,y) x=min(x,(__typeof__(x))y)
#define mxto(x,y) x=max(x,(__typeof__(x))y)
#define INF 1023456789
#define LINF 1023456789123456789
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<pll> vll;
mt19937 rng(time(0));
#define maxn 100005
int n,k,t,x[maxn];
ll a[maxn];
bool check(int s){
for(int i=0;i<n;++i)a[i]=(ll)2*s*t*i-x[i];
int ml=min_element(a,a+k)-a;
int mr=max_element(a+k-1,a+n)-a;
int l=k-1,r=k-1;
ll cl=a[l],cr=a[r];
while(l>ml||r<mr){ //try expanding outwards
bool move=false;
while(l>ml&&a[l-1]<=cr)cl=min(cl,a[--l]),move=true;
while(r<mr&&cl<=a[r+1])cr=max(cr,a[++r]),move=true;
if(!move)return false;
}
l=0,r=n-1;
cl=a[l],cr=a[r];
if(cl>cr)return false;
while(l<ml||r>mr){
bool move=false;
while(l<ml&&a[l+1]<=cr)cl=min(cl,a[++l]),move=true;
while(r>mr&&cl<=a[r+1])cr=max(cr,a[--r]),move=true;
if(!move)return false;
}
return true;
}
int main(){
sf("%d%d%d",&n,&k,&t);
for(int i=0;i<n;++i)sf("%d",&x[i]);
int lo=0,hi=1e9/t,mid,res;
while(lo<=hi){
mid=(lo+hi)/2;
if(check(mid)){
res=mid;hi=mid-1;
}
else lo=mid+1;
}
pf("%d\n",res);
}
