N, M = gets.split.map(&:to_i)
A = gets.split.map(&:to_i)

def f(x)
  stock = 0
  cost = x * M

  A.each do |a|
    return false if (a + stock) < cost

    if cost <= a
      stock += a - cost
    else
      r = cost - a
      stock -= r
    end
  end

  true
end

ok = 0
ng = 10 ** 18

while (ok - ng).abs >= 2
  x = (ok + ng) / 2

  if f(x)
    ok = x
  else
    ng = x
  end
end

puts ok