#include <stdio.h>
#define N 1000000
#define INF 0x3f3f3f3f
unsigned int X = 12345;
int rand_() {
return (X *= 3) >> 1;
}
void sort(int *xx, int l, int r) {
while (l < r) {
int i = l, j = l, k = r, x = xx[l + rand_() % (r - l)], tmp;
while (j < k)
if (xx[j] == x)
j++;
else if (xx[j] < x) {
tmp = xx[i], xx[i] = xx[j], xx[j] = tmp;
i++, j++;
} else {
k--;
tmp = xx[j], xx[j] = xx[k], xx[k] = tmp;
}
sort(xx, l, i);
l = k;
}
}
int solve(int *xx, int n, int a, int b, int d) {
static char dp[N + 1];
int i, i_, j;
dp[0] = 1;
for (i = 0, i_ = -1, j = 1; j <= n; j++) {
if (j >= a && dp[j - a])
i_ = j - a;
while (i < n && (j - i > b || xx[j - 1] - xx[i] > d))
i++;
dp[j] = i_ >= i;
}
return dp[n];
}
int main() {
static int xx[N];
int n, a, b, i, lower, upper, d;
scanf("%d%d%d", &n, &a, &b);
for (i = 0; i < n; i++)
scanf("%d", &xx[i]);
sort(xx, 0, n);
lower = -1, upper = INF;
while (upper - lower > 1) {
d = (lower + upper) / 2;
if (solve(xx, n, a, b, d))
upper = d;
else
lower = d;
}
printf("%d\n", upper);
return 0;
}
