program factorial;
 var f: text;
     i: longword;
     s,p: qword;
 begin
   assign(f,'fact.in'); reset(f);
    read(f,p);
   Close(f);

   assign(f,'fact.out'); rewrite(f);

   s:=0;
   case p of
      1: write(f,5);
      2: write(f,10);
      3: write(f,15);
      4: write(f,20);
      5: write(f,-1);
   else begin
          write(f,(p-1)*5);
        end;
   end;
   Close(f);
 end.