function eks = ks(kk)
k=[];
 k = kk;
 l=size(kk);%mencari ukuran kata kunci
 %melakukan ekstrak huruf yang sama
 for i=1:l(1,2)-1
    if double(k(i))~=32
        for j=i+1 : l(1,2)
            if k(i) == k(j)
                k(j)='@';
            end
        end
    else
        k(i) = '@';
    end
 end
 %menampilkan hasil ekstrak
 j=1;
 for i =1 : l(1,2)
     if k(i)~='@'
         eks(j) = k(i);
         j = j+1;
     end
     l = size(k);
 end

 %buat pemetaan kunci
 for i = 1 : 26
     map(1,i) = char(96+i);
 end
 l = size(eks);
 %fprintf('%d',l);
 
 mapsem = map(1,:);
 x=0;
 for i = 1 : 26
     for j = 1 : l(1,2)
         if mapsem(i) == eks(j)
             mapsem(i)='@';
             x= x+1;
         end
     end
 end
 %fprintf('%s\n',mapsem);
 for i = 1 : 26
     if mapsem(i) ~= '@'
         eks(x+1) = mapsem(i);
         x = x+1;
     end
 end
return