#include <bits/stdc++.h>
#define fast ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL)
#define ll long long int
#define ld long double
using namespace std;
const int N = 2e3 + 5;
const int MOD = 1e9 + 7;
int n, p, q, a[N], dp[N][N], top[N], toq[N];
int go(int i, int small, ll mid){
if(small > p) return INT_MAX;
if(i == n + 1) return 0;
if(dp[i][small] != -1)
return dp[i][small];
int req = INT_MAX;
req = min(req, go(top[i], small + 1, mid));
req = min(req, go(toq[i], small, mid) + 1);
return dp[i][small] = req;
}
bool check(ll mid){
// let dp[i][j] denote the min no. of large cameras needed when we place atmost j small cameras
// in the prefix of i.
memset(dp, -1, sizeof dp);
for(int i = 1; i <= n; ++i){
int low = i + 1, high = n, res = n + 1;
while(low <= high){
int mid1 = (low + high) / 2;
if(a[mid1] > a[i] + mid - 1){
res = mid1;
high = mid1 - 1;
}
else
low = mid1 + 1;
}
top[i] = res;
low = i + 1, high = n, res = n + 1;
while(low <= high){
int mid1 = (low + high) / 2;
if(a[mid1] > a[i] + 2*mid - 1){
res = mid1;
high = mid1 - 1;
}
else
low = mid1 + 1;
}
toq[i] = res;
}
return (go(1, 0, mid) <= q);
}
void solve(){
cin >> n >> p >> q;
for(int i = 1; i <= n; ++i)
cin >> a[i];
if(p + q >= n){
cout << "1\n";
return;
}
sort(a + 1, a + n + 1);
ll low = 1, high = 1e12, ans;
while(low <= high){
ll mid = low + (high - low) / 2;
if(check(mid)){
ans = mid;
high = mid - 1;
}
else
low = mid + 1;
}
cout << ans << "\n";
}
int main(){
fast;
int t = 1;
// cin >> t;
while(t--)
solve();
return 0;
}
