#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
#define y1 zck_is_king
#define pii pair<int, int>
#define ull unsigned ll
#define f first
#define s second
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
#define SQ(x) (x)*(x)
#define MN(a,b) a = min(a,(__typeof__(a))(b))
#define MX(a,b) a = max(a,(__typeof__(a))(b))
#define pb push_back
#define REP(i,n) for (int i = 0; i<n; ++i)
#define RREP(i,n) for (int i = n-1; i>=0; --i)
#define REP1(i,n) for (int i = 1; i<=n; ++i)
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#ifdef BALBIT
#define IOS()
#define bug(...) fprintf(stderr,"#%d (%s) = ",__LINE__,#__VA_ARGS__),_do(__VA_ARGS__);
template<typename T> void _do(T &&x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T &&x, S &&...y){cerr<<x<<", ";_do(y...);}
#else
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define bug(...)
#endif
const int iinf = 1e9+10;
const ll inf = 2e18+10000;
const ll mod = 1e9+7 ;
void GG(){cout<<"0\n"; exit(0);}
ll mpow(ll a, ll n, ll mo = mod){ // a^n % mod
ll re=1;
while (n>0){
if (n&1) re = re*a %mo;
a = a*a %mo;
n>>=1;
}
return re;
}
ll inv (ll b, ll mo = mod){
if (b==1) return b;
return (mo-mo/b) * inv(mo%b,mo) % mo;
}
const int maxn = 1e6+5;
int n,k,T;
bool spread(vector<ll> a) {
int n = SZ(a);
int Lp=k, Rp=k;
//
REP(i, k+1) {
if (a[i] > a[Lp]) Lp = i;
}
for (int i = k; i<n; ++i) {
if (a[i] < a[Rp]) Rp = i;
}
bug(Lp, Rp);
// try to spread [k,k] to [Lp, Rp], maintaining a[L] >= a[R]
int nowl = k, nowr = k;
int lcan = k, rcan = k; // where l,r can go as of now (but not peaks)
bool chg = 1;
while (chg) {
chg = 0;
while (Lp < lcan) {
// bug(lcan, rcan);
if (a[lcan-1] >= a[nowr] ) {
--lcan;
if (a[lcan] >= a[nowl]) {
nowl = lcan; chg = 1;
}
}else break;
}
while (rcan < Rp) {
if (a[rcan+1] <= a[nowl]) {
++rcan;
if (a[rcan] <= a[nowr]) {
nowr = rcan; chg = 1;
}
}else break;
}
bug(lcan, rcan);
}
bug(nowl, nowr, Lp, Rp);
if (nowl != Lp || nowr != Rp) return 0;
if (a[0] < a[n-1]) return 0;
nowl = 0, nowr = n-1; // spreading backwards now
lcan = 0, rcan = n-1;
chg = 1;
// bug("hey");
while (chg) {
chg = 0;
while (lcan < Lp) {
if (a[lcan+1] >= a[nowr]) {
++lcan;
if(a[lcan] >= a[nowl]) {
nowl = lcan; chg = 1;
}
}else break;
}
while (rcan > Rp) {
if (a[rcan-1] <= a[nowl]) {
--rcan;
if (a[rcan] <= a[nowr]) {
nowr = rcan; chg = 1;
}
}else break;
}
bug(lcan, rcan);
}
// if (a[nowr] > a[rcan]) assert(0);
bug(nowl, nowr, lcan, rcan, Lp, Rp);
if (nowl != Lp || nowr != Rp) return 0;
return 1;
}
signed main(){
IOS();
cin>>n>>k>>T;
--k;
vector<ll> X(n);
REP(i,n) {
cin>>X[i];
}
// for (int x : L) bug(x);
// for (int x : R) bug(x);
// bug(st);
ll l = 0, r = 1e9+5;
while (l!=r) {
ll s = (l+r)/2;
if (s * T * 2> 1000000000ll * 2) {
r = s; continue;
}
vector<ll> a(n);
REP(i,n) {
a[i] = X[i] - 2 * s * T * i;
}
bug(l,r, s);
bool ok = spread(a);
if (!ok) {
l = s+1;
}else{
r = s;
}
}
cout<<l<<endl;
}
