title: Negative dimension size caused by subtracting 3 from 1 for 'conv2d_2/convolution'
body: <p>I got this error message when declaring the input layer in Keras.</p>
  
  <blockquote>
    <p>ValueError: Negative dimension size caused by subtracting 3 from 1 for
    'conv2d_2/convolution' (op: 'Conv2D') with input shapes: [?,1,28,28],
    [3,3,28,32].</p>
  </blockquote>
  
  <p>My code is like this</p>
  
  <pre><code>model.add(Convolution2D(32, 3, 3, activation='relu', input_shape=(1,28,28)))
  </code></pre>
  
  <p>Sample application: <a href="https://github.com/IntellijSys/tensorflow/blob/master/Keras.ipynb" rel="noreferrer">https://github.com/IntellijSys/tensorflow/blob/master/Keras.ipynb</a></p>