#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 2e3 + 7, inf = 1e9 + 7;
int n, mn, mx, a[mxN], dp[mxN][mxN];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//freopen(task".INP", "r", stdin);
//freopen(task".OUT", "w", stdout);
cin >> n >> mn >> mx;
for (int i = 1; i <= n; i++)
cin >> a[i];
sort(a + 1, a + n + 1);
mx = min(n, mx);
int l = 1, r = inf, ans = inf;
while (l <= r)
{
int mid = (l + r) / 2;
for (int i = 1; i <= n + 1; i++)
{
for (int j = 0; j <= mx; j++)
dp[i][j] = -inf;
}
dp[1][mx] = mn;
for (int i = 1; i <= n; i++)
{
for (int j = 0; j <= mx; j++)
{
if (dp[i][j] == -inf)
continue;
if (j)
{
int tmp = upper_bound(a + 1, a + n + 1, a[i] + 2 * mid - 1) - a;
dp[tmp][j - 1] = max(dp[tmp][j - 1], dp[i][j]);
}
if (dp[i][j])
{
int tmp = upper_bound(a + 1, a + n + 1, a[i] + mid - 1) - a;
dp[tmp][j] = max(dp[tmp][j], dp[i][j] - 1);
}
}
}
bool con = 0;
for (int i = 0; i <= mx; i++)
con |= (dp[n + 1][i] != -inf);
if (con)
{
ans = mid;
r = mid - 1;
}
else
l = mid + 1;
}
cout << ans;
}
