def dice_calc(x, y):
    """calculates dice coefficients 2 lists of mutated gene names (x, y)"""
    x_and_y = [gene for gene in x if gene in y]
    if len(x) <= 0 or len(y) <=0:
        return -1
    dice_value = (2.0 * len(x_and_y)) / (len(x) + len(y))
    return dice_value