int Foo(int[] arr1, int[] arr2) {
    Array.Sort(arr2);
    Dictionary<(int, int), int> dictionary = new Dictionary<(int, int), int>();

    int Bar(int i, int prev) {
        if (i == arr1.Length) return 0;
        if (dictionary.ContainsKey((i, prev))) return dictionary[(i, prev)];

        int cost = int.MaxValue;
        if (arr1[i] > prev) {
            cost = Bar(i + 1, arr1[i]);
        }
        
        int idx = Array.BinarySearch(arr2, prev + 1);
        if (idx < 0) idx = ~idx;
        if (idx < arr2.Length) {
            cost = Math.Min(cost, 1 + Bar(i + 1, arr2[idx]));
        }

        dictionary[(i, prev)] = cost;
        return cost;
    }

    int result = Bar(0, int.MinValue);
    return result == int.MaxValue ? -1 : result;
}

int[] arr1 = {1, 5, 3, 6, 7};
int[] arr2 = {1, 3, 2, 4};
int result = Foo(arr1, arr2);
Console.WriteLine(result);