SHA-256

# Updated 2011 to work with latest 1.9 (force_encoding)

# Helper method
class Integer
  def rotate(n=1)
    self >> n | self << (32 - n)
  end
end

# Input
input = gets(nil) || ''

if RUBY_VERSION >= '1.9'
  input = input.force_encoding('US-ASCII')
end

# Note 1: All variables are unsigned 32 bits and wrap modulo 232 when calculating
# Note 2: All constants in this pseudo code are in big endian

# Initialize variables
# (first 32 bits of the fractional parts of the square roots of the first 8 primes 2..19):
z = 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19

# Initialize table of round constants
# (first 32 bits of the fractional parts of the cube roots of the first 64 primes 2..311):
k =
   0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
   0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
   0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
   0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
   0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
   0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
   0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
   0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2

# Pre-processing:
# append the bit '1' to the message
# append k bits '0', where k is the minimum number >= 0 such that the resulting message
#    length (in bits) is congruent to 448 (mod 512)
# append length of message (before pre-processing), in bits, as 64-bit big-endian integer
length = input.length*8
input << 128
input << 0 while input.size%64 != 56
input += [length].pack('Q').reverse

# Process the message in successive 512-bit chunks:
input.unpack('C*').each_slice(64){|chunk|
  w = []
  chunk.each_slice(4){|a,b,c,d| w << (((a<<8|b)<<8|c)<<8|d) }

  # Extend the sixteen 32-bit words into sixty-four 32-bit words:
  (16..63).map{|i|
    s0 = w[i-15].rotate(7) ^ w[i-15].rotate(18) ^ (w[i-15] >> 3)
    s1 = w[i-2].rotate(17) ^ w[i-2].rotate(19) ^ (w[i-2] >> 10)
    w[i] = w[i-16] + s0 + w[i-7] + s1 & 0xffffffff
  }

  # Initialize hash value for this chunk:
  a,b,c,d,e,f,g,h = z

  # Main loop:
  (0..63).each{|i|
    s0  = a.rotate(2) ^ a.rotate(13) ^ a.rotate(22)
    maj = (a & b) ^ (a & c) ^ (b & c)
    t2  = s0 + maj & 0xffffffff
    s1  = e.rotate(6) ^ e.rotate(11) ^ e.rotate(25)
    ch = (e & f) ^ ((~e) & g)
    t1 = h + s1 + ch + k[i] + w[i] & 0xffffffff

    h = g
    g = f
    f = e
    e = d + t1 & 0xffffffff
    d = c
    c = b
    b = a
    a = t1 + t2 & 0xffffffff
  }

  # Add this chunk's hash to result so far:
  z[0] = z[0] + a & 0xffffffff
  z[1] = z[1] + b & 0xffffffff
  z[2] = z[2] + c & 0xffffffff
  z[3] = z[3] + d & 0xffffffff
  z[4] = z[4] + e & 0xffffffff
  z[5] = z[5] + f & 0xffffffff
  z[6] = z[6] + g & 0xffffffff
  z[7] = z[7] + h & 0xffffffff
}

# Produce the final hash value (big-endian)
hash = '%.8x'*8 % z

# Output
puts hash