Having problem in using or statement in switch case

Problem: "Return the number of days in a given month in 2017. If the input is not a valid month number, return -1.

You cannot use IF statements"

Where is the problem in my code.How can I use or statement in switch case?

Firsly I tried case as number but it didn't work

then I tried as character but it also didn't work

function d = daysInMonth(m)
x=[31 28 31 30 31 30 31 31 30 31 30 31];
c = num2str(m);
switch c
    case '1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'|'10'|'11'|'12'
d=x(m);
    otherwise
        d=-1;
end
end

Answer 1

[Walter Roberson]

    case {'1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12'}
        

However, you do not need to convert to character vector.

     switch m
         case {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
     end

[Arif Istiak Abeg]

I tried this code also but didn,t work

then I used 'case" for 12 line indiviually it worked but the code became longer