def prmCn(N):
    if N < 2:
        return -1
    if N < 4:
        return 1
    pa = [i for i in range(5, N+1, 2) if i % 3]
    pr = [2, 3]
    rN = int(N**0.5)
    while True:
        m = pa[0]
        if m >= rN:
            break
        pr += [m]
        pa = [n for n in pa[1:] if n % m]
    pr += pa
    pa = [1]+[0]*N
    for r in pr:
        for j in range(N, -1, -1):
            if pa[j] > 0 and j+r <= N:
                pa[j+r] = max(pa[j+r], pa[j]+1)
    return pa[N]-1


N = int(input())
print(prmCn(N))