def pairs(boys, girls, diff, x=False):
    a = 0
    to_return = 0
    if len(boys) == 0 and len(girls) == 0:
        if x == False:
            return 0
        return 0
    for index1, value1 in enumerate(boys):
        for index2, value2 in enumerate(girls):
            if abs(value2-value1) <= diff:
                #print boys[0:index1] + boys[index1 + 1:], girls[0:index2] + girls[index2 + 1:]
                a = 1 + pairs(boys[0:index1] + boys[index1 + 1:],girls[0:index2] + girls[index2 + 1:], diff , True)
        if to_return<a:
            to_return = a
    return to_return