#include <bits/stdc++.h>
#define pb push_back
#define SZ(x) ((int) x.size())
#define all(x) x.begin(), x.end()
#define ld long double
#define ll long long
using namespace std;
const int N = 1e5 + 111;
const ld INF = 1e17;
int n, k;
ld T, X[N];
vector <ld> a[2], ps[2]; int mxn[2], p[2], nxt[2]; ld mn[2];
ld g(int x) {
return ps[x][p[x]];
}
void go_next(int x) {
nxt[x] = p[x] + 1;
mn[x] = INF;
while (nxt[x] <= mxn[x] && ps[x][nxt[x]] < ps[x][p[x]]) {
mn[x] = min(mn[x], ps[x][nxt[x]]);
nxt[x]++;
}
}
void set_next(int x) {
p[x] = nxt[x];
go_next(x);
}
bool check2() {
for (int i = 0; i < 2; i++) {
p[i] = nxt[i] = mn[i] = 0;
}
if (g(0) + g(1) < 0) return 0;
go_next(0);
go_next(1);
while (nxt[0] <= mxn[0] || nxt[1] <= mxn[1]) {
if (nxt[0] <= mxn[0] && mn[0] + g(1) >= 0ll) {
set_next(0);
}
else if (nxt[1] <= mxn[1] && mn[1] + g(0) >= 0) {
set_next(1);
}
else return 0;
}
return 1;
}
bool check(int s) {
a[0].clear(), a[1].clear();
a[0].pb(T);
for (int i = k + 1; i < n; i++) {
a[0].pb(-(X[i] - X[i - 1]) * 1. / (2 * s));
a[0].pb(T);
}
for (int i = k - 1; ~i; i--) {
a[1].pb(-(X[i + 1] - X[i]) * 1. / (2 * s));
a[1].pb(T);
}
ps[0].clear();
ps[1].clear();
for (int i = 0; i < 2; i++) {
ps[i].pb(0);
for (auto j: a[i]) {
ps[i].pb(ps[i].back() + j);
}
mxn[i] = max_element(all(ps[i])) - ps[i].begin();
}
bool ans = check2();
for (int i = 0; i < 2; i++) {
reverse(all(ps[i]));
mxn[i] = SZ(ps[i]) - 1 - mxn[i];
}
ans = ans & check2();
return ans;
}
void solve() {
if (X[n - 1] == 0) {
cout << 0;
return;
}
int L = 0, R = 1e9 + 1;
while (L + 1 < R) {
int m = (L + R) / 2;
if (check(m)) {
R = m;
}
else {
L = m;
}
}
cout << R;
}
void read() {
cin >> n >> k >> T;
k--;
for (int i = 0; i < n; i++) {
cin >> X[i];
}
}
int main() {
ios::sync_with_stdio(0), cin.tie(0);
read();
solve();
}
