#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 1e5 + 10;
ll n, k, t, x[MAXN], pt1, pt2, pt3, pt4, sum1, sum2, sum;
vector<ll> h1, h2;
void input() {
cin >> n >> k >> t;
--k;
for (int i = 0; i < n; i++)
cin >> x[i];
}
void setup(ll s) {
pt1 = pt2 = pt3 = pt4 = sum = sum1 = sum2 = 0;
h1.clear();
h2.clear();
for (int i = k; i > 0; i--)
h1.push_back(x[i] - x[i - 1] - s);
for (int i = k + 1; i < n; i++)
h2.push_back(x[i] - x[i - 1] - s);
}
void move() {
while (pt3 < h1.size() && (sum >= sum1 && sum1 >= 0)) {
sum1 += h1[pt3];
pt3++;
}
while (pt4 < h2.size() && (sum >= sum2 && sum2 >= 0)) {
sum2 += h2[pt4];
pt4++;
}
}
bool check(ll s) {
setup(s);
while (pt1 < h1.size() || pt2 < h2.size()) {
move();
//cerr << pt1 << " , " << pt3 << " ::: " << pt2 << " , " << pt4 << " ::: " << sum << endl;
if (pt1 != h1.size() && (sum >= sum1 && sum1 < 0)) {
sum -= sum1;
sum1 = 0;
pt1 = pt3;
continue;
}
if (pt2 != h2.size() && (sum >= sum2 && sum2 < 0)) {
sum -= sum2;
sum2 = 0;
pt2 = pt4;
continue;
}
if ((pt1 != h1.size() && sum < sum1) || (pt2 != h2.size() && sum < sum2))
return false;
return (sum >= sum1 + sum2);
}
return true;
}
ll findAns() {
ll l = -1, r = x[n - 1];
while (r - l > 1) {
ll mid = (l + r) / 2;
if (check(2 * mid * t))
r = mid;
else
l = mid;
}
return r;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
input();
cout << findAns() << endl;
return 0;
}
