static int walk(int[] array) {
	int[] t = new int[array.length];
	Arrays.fill(t, -1);
	t[0] = 0;
	for (int i = 0; i < array.length; i&#43;&#43;) {
		int d = array[i];
		if (d <= 0 || t[i] < 0)
			continue;
		for (int j = i &#43; 1; j <= i &#43; d && j < array.length; j&#43;&#43;) {
			t[j] = t[j] == -1 ? t[i] &#43; 1 : Math.min(t[j], t[i] &#43; 1);
		}
	}
	return t[array.length - 1] >= 0 ? t[array.length - 1]
			: -1;
}