import sys
stdin=sys.stdin

ip=lambda: int(sp())
fp=lambda: float(sp())
lp=lambda:list(map(int,stdin.readline().split()))
sp=lambda:stdin.readline().rstrip()
yp=lambda:print('Yes')
np=lambda:print('No')

def primes(n):
    is_prime = [True] * (n + 1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, int(n**0.5) + 1):
        if not is_prime[i]:
            continue
        for j in range(i * 2, n + 1, i):
            is_prime[j] = False
    return [i for i in range(n + 1) if is_prime[i]]

n=ip()
sosuu=primes(n)
dp=[0 for _ in range(20001)]
for i in range(len(sosuu)):
    for j in range(20000,-1,-1):
        if j==0:
            dp[j+sosuu[i]]=max(dp[j+sosuu[i]],1)
        else:
            if 0<=j-sosuu[i] and dp[j-sosuu[i]]!=0:
                dp[j]=max(dp[j],dp[j-sosuu[i]]+1)

if dp[n]==0:
    print(-1)
else:
    print(dp[n])