Minimum period of a signal What is the minimum period P (in samples) of the signal $e^{j(\frac{M}{N} )*2πn}$ for the following values of M and N?

M=1,N=3
M=5,N=7
M=35,N=15

I have got the answer for the first pair of values, which is 3. But I could not get the other two correct. Please help.
It's already answered in the comments so just to close it out: the answers are 3, 7 and 3. The periodicity is basically given by the denominator of the fraction in front of 2*pi*n after the fraction has been simplified (no common divisors between nominator and denominator).  The simplified fractions for the cases are 1/3, 5/7 and 7/3 so the periodicity is 3, 7 and 3 respectively.