Hi there! When I try the following code

data = {1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5}
FindClusters[data]

I get the error

FindClusters::wrgdist: The distance function EuclideanDistance cannot be comuputed on the data. 

Any other distance function gives a similar error. Same error for more complicated data. Does anyone know, what is wrong here?

In the end I would like to cluster data of the form {a,b}, where a means the number of hours a teacher works per week and b means the number of hours in the afternoon, or the number of free days etc. If you have any valuable ideas, you are very welcome to point them out to me (since I am only a sparse user of Mathematica). Thank you!