title: Proof for number of internal nodes in a tree
body: <p>I was reading about compressed tries and read the following:</p>
  
  <p>a compressed trie is a tree which has L leaves and every internal node in the trie has at least 2 children. </p>
  
  <p>Then the author wrote that a tree with L leaves such that every internal node has alteast 2 children, has atmost L-1 internal nodes. I am really confused why this is true.</p>
  
  <p>Can somebody offer a inductive proof for it?</p>