N = int(input())

dat = [0] * (N + 1)
C = N + 1
prime = []
for i in range(2,C):
    if dat[i] == 0:
        for j in range(2 * i,C,i):
            dat[j] = 1
        prime.append(i)
n = len(prime)
dp = [[-1] * (N + 1) for _ in range(n+1)]
dp[0][0] = 0
_sum = 0

for i in range(n):
    p = prime[i]
    for j in range(_sum+1):
        dp[i+1][j] = dp[i][j]
    for j in range(_sum+1):
        if j + p <= N:
            dp[i+1][j+p] = max(dp[i+1][j+p],dp[i][j] + 1)
        else:
            break
    _sum = min(N,_sum+p)
if dp[-1][-1] == 0:
    print(-1)
else:
    print(dp[-1][-1])