Fermat's little Theorem-Help

What a gap ........ :(

Let us assume the contrary....
Suppose two quantities 'ma' and 'na' leave the same remainder r when divided by p....
ma = cp + r ; na = dp + r [m≠n]
(m-n)a = (c-d)p....
Therefore p divides (m-n)a...
Since a and p are coprime....p divides (m-n)
But this is not possible since m and n are unequal and both are less than p
Q.E.D

Thanks for the help.........I get it now