#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ii pair<ll,ll>
#define fi first
#define se second
#define endl '\n'
#define puf push_front
#define pof pop_front
#define pub push_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound
#define rep(x,s,e) for (auto x=s-(s>e);x!=e-(s>e);s<e?x++:x--)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n,k,t;
ll arr[100005];
ii memo[1005][1005];
bool can(ll i){
rep(x,0,1005) rep(y,0,1005) memo[x][y]=ii(1e10,-1e10);
memo[k][k]=ii(arr[k]-i,arr[k]+i);
rep(x,0,n-1){
rep(y,1,n-x+1){
int l=y,r=y+x;
ii temp=memo[l][r];
temp.fi=max(temp.fi,arr[l-1]-(x+1)*i);
temp.se=min(temp.se,arr[l-1]+(x+1)*i);
if (temp.fi<=temp.se){
memo[l-1][r].fi=min(memo[l-1][r].fi,temp.fi-i);
memo[l-1][r].se=max(memo[l-1][r].se,temp.se+i);
}
temp=memo[l][r];
temp.fi=max(temp.fi,arr[r+1]-(x+1)*i);
temp.se=min(temp.se,arr[r+1]+(x+1)*i);
if (temp.fi<=temp.se){
memo[l][r+1].fi=min(memo[l][r+1].fi,temp.fi-i);
memo[l][r+1].se=max(memo[l][r+1].se,temp.se+i);
}
}
}
return memo[1][n].fi<=memo[1][n].se;
}
int main(){
cin.tie(0);
cout.tie(0);
cin.sync_with_stdio(false);
cin>>n>>k>>t;
rep(x,1,n+1) cin>>arr[x];
ll lo=-1,hi=1e9,mi;
while (hi-lo>1){
mi=hi+lo>>1;
if (can(mi)) hi=mi;
else lo=mi;
}
cout<<(hi+t-1)/t<<endl;
}
