#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2005;
const int MAXX = 1e5 + 5;
int n;
int a[MAXN];
int p, q;
int cost[MAXN][MAXN];
int dp[MAXN][MAXX];
int tinh(int w)
{
for (int j = 0; j <= p; j++)
{
dp[0][j] = 0;
}
for (int i = 1; i <= n; i++)
{
for (int j = 0; j <= p; j++)
{
dp[i][j] = INT_MAX;
}
}
for (int i = 1; i <= n; i++)
{
int pos1 = i;
while (pos1 > 1 and a[i] - a[pos1 - 1] + 1 <= w)
{
pos1--;
}
int pos2 = pos1;
while(pos2 > 1 and a[i] - a[pos2 - 1] + 1 <= 2 * w)
{
pos2--;
}
for (int j = 0; j <= p; j++)
{
if (dp[pos2 - 1][j] != INT_MAX)
{
dp[i][j] = min(dp[i][j], dp[pos2 - 1][j] + 1);
}
if (j > 0 and dp[pos1 - 1][j - 1] != INT_MAX)
{
dp[i][j] = min(dp[i][j], dp[pos1 - 1][j - 1]);
}
}
}
int res = INT_MAX;
for (int i = 0; i <= p; i++)
{
res = min(res, dp[n][i]);
}
return res;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> p >> q;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
}
sort(a + 1, a + n + 1);
int l = 0;
int r = INT_MAX;
int ans = -1;
while(l <= r)
{
int mid = (l + r) / 2;
if (tinh(mid) <= q)
{
ans = mid;
r = mid - 1;
}
else
{
l = mid + 1;
}
}
cout << ans;
}
