let input = readLine()!.characters.split(" ").map{Int(String($0))!}
let (N,C,K) = (input[0],input[1],input[2])
var ans = 0
var t = Int(1e9)
var c = 0
for _ in 0..<N {
  let T = Int(readLine()!)!
  c += 1
  if t+6 < T || c > C {
    ans += 1
    c = 1
    t = T
  }
}
print(ans)