#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("Ofast,unroll-loops")
using namespace std;
using namespace __gnu_pbds;
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define f first
#define s second
#define int long long
#define ll long long
#define pii pair<int,int>
#define ar array
template<class T>bool umax(T &a,T b){if(a<b){a=b;return true;}return false;}
template<class T>bool umin(T &a,T b){if(b<a){a=b;return true;}return false;}
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
tree_order_statistics_node_update> ordered_set;
const int inf = 1e17 + 7;
const int mod = 1e9 + 7;
const int N = 3e5 + 5;
const int md = 998244353;
int binpow(int a, int b){
if(b == 0)return 1;
if(b % 2 == 0){
int c = binpow(a,b/2);
return (c*c)%mod;
}
return (binpow(a,b-1)*a)%mod;
}
int divi(int a, int b){
return (a*(binpow(b,mod-2)))%mod;
}
int n,m,k;
void solve(){
cin >> n >> m >> k;
vector<int>v(n+1);
for(int i = 1;i<=n;i++)cin >> v[i];
sort(all(v));
if(m+k >= n){
cout << 1 << "\n";
return;
}
//~ for(auto to:v)cout << to << " ";
//~ cout << "\n";
int l = 2, r = 1e9, ans = -1;
while(l <= r){
int mid = (l+r)/2;
bool flag = false;
int dp[m+1][k+1]{};
for(int i = 0;i<=m;i++){
for(int j = 0;j<=k;j++){
if(i >= 1){
int h = v[dp[i-1][j] + 1] + mid - 1;
int u = upper_bound(all(v), h) - v.begin() - 1;
umax(dp[i][j], u);
}
if(j >= 1){
int h = v[dp[i][j-1] + 1] + 2*mid - 1;
int u = upper_bound(all(v), h) - v.begin() - 1;
umax(dp[i][j], u);
}
if(dp[i][j] == n)flag = true;
}
}
if(flag){
r = mid - 1;
ans = mid;
}
else l = mid + 1;
}
cout << ans << "\n";
}
/*
*/
signed main()
{
// freopen("seq.in", "r", stdin);
// freopen("seq.out", "w", stdout);
//~ ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
int tt=1;//cin>>tt;
while(tt--)solve();
}
