#include<bits/stdc++.h>
using namespace std;
#define int long long
const int TAILLE_MAX=1000+5,INFINI=1000*1000*1000;
int nbVal,posInit,tempsInit;
int val[TAILLE_MAX];
int dv[TAILLE_MAX][TAILLE_MAX],pb[TAILLE_MAX][TAILLE_MAX];
vector<int> calcCumu(vector<int> v) {
vector<int> ans={0};
int somCour=0;
for (int i:v) {
somCour+=i;
ans.push_back(somCour);
}
return ans;
}
void DFS(int lig,int col) {
if (pb[lig][col]==0 and dv[lig][col]==0) {
dv[lig][col]=1;
DFS(lig+1,col);
DFS(lig,col+1);
}
}
bool verif(int temps) {
//cout<<temps<<endl;
vector<int> listeGau,listeDro;
for (int i=posInit;i>1;i--) {
listeGau.push_back(2*temps-val[i]+val[i-1]);
}
for (int i=posInit+1;i<=nbVal;i++) {
listeDro.push_back(2*temps-val[i]+val[i-1]);
}
vector<int> cumuGau=calcCumu(listeGau),cumuDro=calcCumu(listeDro);
int tailleGau=cumuGau.size(),tailleDro=cumuDro.size();
for (int i=0;i<=tailleGau;i++) {
for (int j=0;j<=tailleDro;j++) {
pb[i][j]=1;
dv[i][j]=0;
}
}
for (int i=0;i<tailleGau;i++) {
for (int j=0;j<tailleDro;j++) {
if (cumuGau[i]+cumuDro[j]>=0) {
pb[i][j]=0;
}
}
}
/*for (int i:cumuGau) {
for (int j:cumuDro) {
if (i+j>=0) {
cout<<1<<" ";
}
else {
cout<<0<<" ";
}
}
cout<<endl;
}
cout<<endl;*/
DFS(0,0);
return (dv[tailleGau-1][tailleDro-1]==1);
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin>>nbVal>>posInit>>tempsInit;
for (int i=1;i<=nbVal;i++) {
cin>>val[i];
}
int deb=0,fin=INFINI,mid;
while (deb!=fin) {
mid=(deb+fin)/2;
if (verif(mid)) {
fin=mid;
}
else {
deb=mid+1;
}
}
cout<<(deb+tempsInit-1)/tempsInit<<endl;
return 0;
}
