#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
int main(){
cin.sync_with_stdio(0); cin.tie(0);
LL n, k, t;
cin >> n >> k >> t;
k--;
vector<LL> x(n);
for(int i = 0; i < n; i++){
cin >> x[i];
}
LL s = -1;
LL e = 1000000000;
LL dp[n][n];
while(s + 1 < e){
LL m = (s + e) / 2;
vector<LL> y = x;
for(LL i = 0; i < n; i++){
y[i] -= m * t * 2 * i;
}
for(LL i = k; i >= 0; i--){
for(LL j = k; j < n; j++){
dp[i][j] = 0;
if(y[j] <= y[i]){
if((i == k && j == k) || (i < k && dp[i+1][j]) || (j > k && dp[i][j-1])){
dp[i][j] = 1;
}
}
}
}
if(dp[0][n-1]){
e = m;
} else {
s = m;
}
}
cout << e << '\n';
}
