#!/usr/bin/env tclsh

set adapters [split [read stdin]]
while {[lindex $adapters end] eq ""} {set adapters [lrange $adapters 0 end-1]}
set adapters [lsort -integer $adapters]
set adapters [linsert $adapters 0 0]
lappend adapters [expr {3 + [lindex $adapters end]}]

foreach i {1 2 3} {set n($i) 0}

for {set i 0} {$i < [llength $adapters] - 1} {incr i} {
  set delta [expr {[lindex $adapters $i+1] - [lindex $adapters $i]}]
  lappend deltas $delta
  incr n($delta)
}

# parray n
puts "deltas: $deltas"

# There are no deltas of 2 for some reason.
# A delta of 3 gives no choice -- there is just one path.
# A delta of 1 followed by a delta of 3 also gives no choice.
# But consecutive 1s give a choice.  With 2 1s in a row, there are 2 choices.
# For 3 1s in a row, 4 choices.  For 4 1s, 7 choices.

array set map {1 1 2 2 3 4 4 7}

# For all of our deltas, count the number of consecutive 1s.

set prev 3
set len 0
foreach d $deltas {
  if {$d == 1} {
    incr len
  } elseif {$d == 3 && $prev == 1} {
    lappend ones $len
    set len 0
  }
  set prev $d
}
puts "ones: $ones"

# There are no sequences of consecutive 1s greater than 4, so lucky us.

set count 1
foreach i $ones {set count [expr {$count * $map($i)}]}
puts $count