import bisect

def sieve(n):
    if n < 2:
        return []
    sieve = [True] * (n + 1)
    sieve[0] = sieve[1] = False
    for i in range(2, int(n**0.5) + 1):
        if sieve[i]:
            sieve[i*i : n+1 : i] = [False] * len(sieve[i*i : n+1 : i])
    primes = [i for i, is_prime in enumerate(sieve) if is_prime]
    return primes

def main():
    N = int(input().strip())
    primes = sieve(N)
    if not primes:
        print(-1)
        return
    if N == 2:
        print(1)
        return
    
    # Compute cumulative sums
    cumulative = []
    s = 0
    for p in primes:
        s += p
        cumulative.append(s)
        if s > N:
            break
    
    max_m = 0
    for i in range(len(cumulative)):
        if cumulative[i] <= N:
            max_m = i + 1  # 1-based index
        else:
            break
    
    found = False
    for m in range(max_m, 0, -1):
        sum_m = cumulative[m-1]
        D = N - sum_m
        if D < 0:
            continue
        if D == 0:
            print(m)
            return
        
        initial_primes = primes[:m]
        available_primes = primes[m:]
        available_set = set(available_primes)
        available_sorted = available_primes
        
        # Check single replacement
        for p in initial_primes:
            q = p + D
            if q in available_set and q > p:
                print(m)
                return
        
        # Check pair replacement
        for i_p1 in range(m):
            p1 = initial_primes[i_p1]
            for i_p2 in range(i_p1 + 1, m):
                p2 = initial_primes[i_p2]
                required_sum = p1 + p2 + D
                max_q1 = required_sum - p2 - 1
                if max_q1 < p1 + 1:
                    continue
                
                left = bisect.bisect_right(available_sorted, p1)
                right = bisect.bisect_right(available_sorted, max_q1)
                for q1 in available_sorted[left:right]:
                    q2 = required_sum - q1
                    if q2 in available_set and q2 > p2 and q2 != q1:
                        print(m)
                        return
    
    print(-1)

if __name__ == "__main__":
    main()