def strict(f):

    f = sorted(f, key=lambda x:x[0])

    x = f[0]

    for el in f:
        if el[0] == x[0] and el[1] != x[1]: # se x=x e y!=y
            return False                                     # FALSE
        if el[0] != x[0] and el[1] == x[1]: # se x!=x e y=y
            return False
        x = el

    y=f[0][0]
    for el in f:
        if el[1] < y:
            return False
        y = el[1]
    return True


strict(f)