#include <bits/stdc++.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii ;
typedef pair<ll, ll> pll ;
typedef vector<pii> vii ;
typedef vector<int> veci ;
typedef vector<pll> vll ;
typedef vector<ll> vecll;
// find_by_order order_of_key
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define F first
#define S second
#define pb push_back
#define endl '\n'
#define Mp make_pair
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " = " << x << endl
#define set_dec(x) cout << fixed << setprecision(x);
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("in.txt" , "r" , stdin) ; freopen("out.txt" , "w" , stdout);
#define lb lower_bound
#define ub upper_bound
#define for1(n) for(int i=1;i<=n;i++)
#define for0(n) for(int i=0;i<n;i++)
#define forn(n) for(int i=n;i>0;i--)
#define pq priority_queue <pii, vector<pii>, greater<pii>>
const ll mod = 2e9 ;// 998244353 ;// 1e9+9;
ll inf=1e18;
const int N=1e6+100,L=21,bs=701,NN=1e6;
int B[N],C[N],D[N],E[N],n,m,q;
vector<int>g[N];
ll A[N],t,k;
bool check(ll t){
vector<pll>vec1,vec2,vec3,vec4;
vec3.pb({inf,-inf});vec4.pb({inf,-inf});
for1(k-1)
vec1.pb({A[i+1]-A[i],t*2-(A[i+1]-A[i])});
for(int i=n-1;i>=k;i--)
vec2.pb({A[i+1]-A[i],t*2-(A[i+1]-A[i])});
while(vec1.size()!=0){
pll p=vec1.back();vec1.pop_back();
ll st=p.F;
while(p.S<0 && vec1.size()){
p.F=max(p.F,st-p.S+vec1.back().F);
p.S+=vec1.back().S;
vec1.pop_back();
}
vec3.pb(p);
}
while(vec2.size()!=0){
pll p=vec2.back();vec2.pop_back();
ll st=p.F;
while(p.S<0 && vec2.size()){
p.F=max(p.F,st-p.S+vec2.back().F);
p.S+=vec2.back().S;
vec2.pop_back();
}
vec4.pb(p);
}
ll p=t*2;
while(1){
if(vec3.back().F<=p){
p+=vec3.back().S;
vec3.pop_back();
}
else if(vec4.back().F<=p){
p+=vec4.back().S;
vec4.pop_back();
}
else
break;
}
return (vec3.size()==1 && vec4.size()==1);
}
int main(){
fast_io
cin>>n>>k>>t;
for1(n){
cin>>A[i];
}
ll l=-1,r=mod/t+3;
while(r-l!=1){
ll mid=(l+r)>>1;
if(check(t*mid)==0)l=mid;
else r=mid;
}
cout<<l+1<<endl;
}
