def fact(A):
    c0 = A
    r = 2
    lis = []
    count = 1
    while A != 1:
        if A%r == 0:
            A = A//r
            lis.append(r)
            r = 2
        else:
            r += 1
        if r > int(pow(c0,0.5))+1:
            lis.append(A)
            break
    return(lis)

L = []
n = int(input())
for i in range(2,n+1):
    s = fact(i)
    if len(s) == 1:
        L.append(i)
d = [-1]*(n+1)
d[0] = 0
for x in L:

    for i in range(n+1):
        j = n - i
        if x+j > n:
            pass
        
        elif d[j] != -1:
            d[j+x] = max(d[j+x], d[j]+1)

print(d[-1])