N, D, T = gets.split.take(3).map(&:to_i)
X = gets.split.take(N).map(&:to_i)
A = X.sort.group_by{|x| x % D}
p A.map{|mod, a|
  sum = 0
  last = -1.0/0
  a.map{|n| n / D }.each{|n|
    start = n - T
    sum += 2 * T - [last - start, -1].max
    last = n + T
  }
  sum
}.sum