#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define X first
#define Y second
#define mid ((l+r)>>1)
#define lc id<<1
#define rc lc|1
#define all(x) x.begin(), x.end()
#define SZ(x) int(x.size())
#define mins(a, b) (a = min(a, b))
#define maxs(a, b) (a = max(a, b))
const int MXN = 1e5+5;
using big = __int128_t;
int n, k;
ll t, x[MXN];
big y[MXN];
/*
x[r] - x[l] <= (r-l)*t*s*2
x[r] - r*t*s*2 <= x[l] - l*t*s*2
y[i] = x[i] - i*t*s2
y[r] <= y[l]
*/
bool check(ll s) {
for(int i=1; i<=n; i++) y[i] = x[i] - (big)i*t*s*2;
if(y[1]<y[n]) return 0;
int L=k, R=k;
for(int i=k-1; i>=1; i--)
if(y[i]>=y[L]) L = i;
for(int i=k+1; i<=n; i++)
if(y[i]<=y[R]) R = i;
int l=k, r=k;
big mx=y[k], mn = y[k];
while(L<l || r<R)
if(L<l && y[l-1]>=mn)
maxs(mx, y[--l]);
else if(r<R && mx>=y[r+1])
mins(mn, y[++r]);
else return 0;
l=1, r=n;
mx = y[1], mn = y[n];
while(l<L || R<r)
if(l<L && y[l+1]>=mn)
maxs(mx, y[++l]);
else if(R<r && mx>=y[r-1])
mins(mn, y[--r]);
else return 0;
return 1;
}
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
cin >> n >> k >> t;
for(int i=1; i<=n; i++) cin >> x[i];
int l=0, r=x[n];
while(r-l>1)
(check(mid) ? r : l) = mid;
cout << r << '\n';
return 0;
}
