When we are constructing the network module, how can we determine the input size for fully connected layer after CNN blocks? Should we manually compute the final size after CNN blocks?

For example, for this network module, after layer1 & layer2, we feed the result to fc layer, but why the fc layer input size is `7 * 7 * 32`

? Is the `7x7`

deduced from the formula as described in http://cs231n.github.io/convolutional-networks/?

What I am confused is that this process might be tedious if the network goes deep. Why this can not be deduced automatically?