N = int(input())

# dp[i][j] = i こめの素数までを使って j　を作るときの素数の個数の最大値

is_sosu = [True]*(N+10)
is_sosu[0] = is_sosu[1] = False
sosu = []
for i in range(N+1):
    if is_sosu[i]:
        sosu.append(i)
        for j in range(i*2, N+1, i):
            is_sosu[j] = False

dp = [[-10**10]*(N+1) for _ in range(len(sosu)+1)]
dp[-1][0] = 0
for i in range(len(sosu)):
    for j in range(N+1):
        dp[i][j] = dp[i-1][j]
        if j >= sosu[i]:
            dp[i][j] = max(dp[i][j], dp[i-1][j-sosu[i]]+1)

ans = dp[len(sosu)-1][N]
if ans < 0:
    print(-1)
else:
    print(ans)