A, B, C = map(int, input().split())

# 複数回の会計に分割できる
def calc(a,b,coins):
  if coins <= -9:
    return None
  elif coins < 0:
    
    return None if b == 0 else 1 + calc(a+9, b-1, coins+8) # 1Gに対して10G払う。
  elif coins is 0:
    return 0
  elif a >= 11 and coins >= 10:
    return 1 + calc(a-11, b+1, coins-10) # 11枚1G払ってお釣り10Gもらう
  elif a is 0:
    return coins * 10
  else:
    g1 = min(a, coins)
    return g1 + calc(a-g1, b, coins-g1)
      
print(calc(A, B, A+B-C) or "Impossible")
# 9 17 -1
# 18 16 -1