def No_of_Triangle(N,K):
    
    if (N < K):
        return -1;
    else:
        Tri_up = 0;
        Tri_up = ((N - K + 1) *(N - K + 2)) // 2;
        Tri_down = 0;
        Tri_down = ((N - 2 * K + 1) *(N - 2 * K + 2)) // 2;
        return Tri_up + Tri_down;
def is_not_prime(n):
    import math
    
    result = False
    for i in range(2,int(math.sqrt(n)) + 1):
        if n % i == 0:
            result = True
    return result