title: finding substrings of a string
body: <p>For a string of length n, the formula to compute all the substrings are: n(n+1)/2
  Can someone help me out in intuitively understanding this formula?</p>
  
  <p>Wikipedia says: 
  <em>"The number of substrings of a string of length  where symbols only occur once, is the number of ways to choose two distinct places between symbols to start/end the substring"</em></p>