title: MATLAB simulink error
body: <p>I am trying to simulate a block diagram in simulink. The diagram is as follows :  <img src="https://i.stack.imgur.com/aHKVo.jpg" alt="block diagram"> </p>
  
  <p>When I change the gain to any other value other than 1 I get the following error :</p>
  
  <p><img src="https://i.stack.imgur.com/r0ZcT.jpg" alt="error"></p>
  
  <p>I have tried using unit delay, z inverse delay.When I use them I don't get the error but the output changes.i.e does not match with the output of '>>step(sys)'</p>
  
  <p>Please help.</p>
  
  <p>Thank you.</p>