The number of ways of rolling a dice where no two numbers probability that no one rolls the same number = 6 x 5 x 4 x 3

Now total possibilities of rolling a dice = 64

The probability that a no one gets the same number = 6 $\times$ 5 $\times$ 4$\times$ 364=518

So the probability that at least two people gets same number = 1/518=13/18