#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 1e5 + 10;
ll n, k, t, x[MAXN], X[MAXN];
void input() {
cin >> n >> k >> t;
--k;
for (int i = 0; i < n; i++)
cin >> x[i];
}
bool check(ll s) {
for (ll i = 0; i < n; i++)
X[i] = x[i] - 2 * s * t * i;
ll ma1 = k, ma2 = k;
for (int i = k; i >= 0; i--)
if (X[i] >= X[ma1])
ma1 = i;
for (int i = k; i < n; i++)
if (X[i] <= X[ma2])
ma2 = i;
ll l = k, r = k;
while (true) {
bool has = false;
ll l1 = l;
while (true) {
if (l1 - 1 >= ma1 && X[l1 - 1] >= X[r])
l1--;
else
break;
if (X[l1] >= X[l] || l1 == ma1)
break;
}
if (X[l1] >= X[l] && l1 < l) {
has = true;
l = l1;
}
ll r1 = r;
while (true) {
if (r1 + 1 <= ma2 && X[r1 + 1] <= X[l])
r1++;
else
break;
if (X[r1] <= X[r] || r1 == ma2)
break;
}
if (X[r1] <= X[r] && r1 > r) {
has = true;
r = r1;
}
if (!has)
break;
}
if ((l != ma1 || r != ma2) || X[0] < X[n - 1])
return false;
l = 0; r = n - 1;
while (true) {
bool has = false;
ll l1 = l;
while (true) {
if (l1 + 1 <= ma1 && X[l1 + 1] >= X[r])
l1++;
else
break;
if (X[l1] >= X[l] || l1 == ma1)
break;
}
if (X[l1] >= X[l] && l1 > l) {
has = true;
l = l1;
}
ll r1 = r;
while (true) {
if (r1 - 1 >= ma2 && X[r1 - 1] <= X[l])
r1--;
else
break;
if (X[r1] <= X[r] || r1 == ma2)
break;
}
if (X[r1] <= X[r] && r1 < r) {
has = true;
r = r1;
}
if (!has)
break;
}
return (l == ma1 && r == ma2);
}
ll findAns() {
ll l = -1, r = x[n - 1];
while (r - l > 1) {
ll mid = (l + r) / 2;
if (check(mid))
r = mid;
else
l = mid;
}
return r;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
input();
cout << findAns() << endl;
return 0;
}
