#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
bool is_valid(int n, const vector<int>& v, int max_diff, int a, int b)
{
int g = 0, gstart = 0;
for(int i = 0; i < n; ++i)
{
if(v[i] - v[gstart] > max_diff)
{
if(i - gstart < a) return false;
g++;
gstart = i;
}
}
if(n - gstart < a) return false;
g++;
return g <= (n + b - 1) / b;
}
int main()
{
int n, a, b;
cin >> n >> a >> b;
vector<int> v(n);
for(int i = 0; i < n; i++)
cin >> v[i];
sort(v.begin(), v.end());
int st, dr, ans;
st = 0, dr = ans = v[n - 1] - v[0];
while(st <= dr)
{
int mid = st + (dr - st) / 2;
if(is_valid(n, v, mid, a, b))
{
ans = mid;
dr = mid - 1;
}
else
{
st = mid + 1;
}
}
cout << ans << "\n";
return 0;
}
