import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val N = sc.nextInt()
    when (N) {
        1 -> { println(-1); return }
        2, 3 -> { println(1); return }
    }
    val primes = mutableListOf<Int>(2, 3)
    for (i in 5 until N step 6) primes.add(i)
    for (i in 7 until N step 6) primes.add(i)
    for (i in 5 until N step 6) {
        if (primes.contains(i)) {
            for (j in i*3 until N step i*2) primes.remove(j)
        }
        if (primes.contains(i+2)) {
            for (j in i*3+6 until N step i*2+4) primes.remove(j)
        }
    }

    val dp = Array(N+1, {0})
    for (n in primes) {
        for (i in N-n downTo 0) if (dp[i] > 0) dp[i+n] = Math.max(dp[i+n], dp[i]+1)
        dp[n] = Math.max(dp[n], 1)
    }
    println(if (dp[N] > 0) dp[N] else -1)
}