default = -100000
n = int(raw_input())
primes = [100000]
lst = [0 if (i == 0 or i == 1) else 1 for i in range(n + 1)]
for i in range(n + 1):
  if lst[i]:
    primes.append(i)
    for j in range(i * 2,n + 1,i):
      lst[j] = 0
dp = [[1 if i == primes[j] else default for j in range(len(primes))] for i in range(n + 1)] 
for i in range(2,n + 1):
  for j in range(1,len(primes)):
    if i == 0 or i == 1 or j == 0:
      dp[i][j] = 0
    elif i >= primes[j]:
      dp[i][j] = max(dp[i][j],dp[i][j - 1], dp[i - primes[j]][j - 1] + 1)
    else:
      dp[i][j] = dp[i][j - 1]
if dp[n][len(primes) - 1] < 0:
  print -1
else:
  print dp[n][len(primes) - 1]