#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2010;
int N, P, Q;
int A[MAXN];
int dp[MAXN][MAXN];
int nxtLarge[MAXN];
int nxtSmall[MAXN];
bool isGood(int w) {
for (int i = 0, j = 0; i < N; i++) {
while (j < N && 0ll + A[i] + w - 1 >= A[j]) j++;
nxtSmall[i] = j;
}
for (int i = 0, j = 0; i < N; i++) {
while (j < N && 0ll + A[i] + 2*w - 1 >= A[j]) j++;
nxtLarge[i] = j;
}
memset(dp, 0, sizeof(dp));
for (int a = 0; a <= P; a++) {
for (int b = 0; b <= Q; b++) {
int cur = dp[a][b];
if (cur == N) return true;
dp[a+1][b] = max(dp[a+1][b], nxtSmall[cur]);
dp[a][b+1] = max(dp[a][b+1], nxtLarge[cur]);
}
}
return false;
}
int main() {
ios::sync_with_stdio(0), cin.tie(0);
cin >> N >> P >> Q;
for (int i = 0; i < N; i++) {
cin >> A[i];
}
sort(A, A + N);
if (P >= N || Q >= N) {
cout << -1 << '\n';
exit(0);
}
int mi = 0;
int ma = int(1e9);
while (ma - mi > 1) {
int md = (mi + ma) / 2;
if (isGood(md)) {
ma = md;
} else {
mi = md;
}
}
cout << ma << '\n';
return 0;
}
