MATLAB: How can i put cell value in a vector

Question

U =

1×2 cell array

[1×2 double] [1×2 double]

U contains these values in cell

U{1}

ans =

1 2

U{2}

ans =

2 3

s= []

I want to put the elements of U in s without duplicate value so I use this instruction: s=unique([U{:}])

this error "Cell contents reference from a non-cell array object." appear,

Answer 1

s=unique(cell2mat(U))