search for 44
  probe 1: left= 1 right=15 mid= 8 A[mid]=31  too small -> left=9
  probe 2: left= 9 right=15 mid=12 A[mid]=51  too big   -> right=11
  probe 3: left= 9 right=11 mid=10 A[mid]=40  too small -> left=11
  probe 4: left=11 right=11 mid=11 A[mid]=44  equal -> found at 11
  result: 11
search for 20
  probe 1: left= 1 right=15 mid= 8 A[mid]=31  too big   -> right=7
  probe 2: left= 1 right= 7 mid= 4 A[mid]=15  too small -> left=5
  probe 3: left= 5 right= 7 mid= 6 A[mid]=22  too big   -> right=5
  probe 4: left= 5 right= 5 mid= 5 A[mid]=19  too small -> left=6
  window empty (left=6 > right=5) -> NIL
  result: 0
