import java.io.PrintWriter
import java.lang.Math.abs
import java.math.BigDecimal
import java.math.BigInteger
import java.util.*
import kotlin.math.max
import kotlin.math.min

@JvmField val INPUT = System.`in`
@JvmField val OUTPUT = System.out
@JvmField val cin = INPUT.bufferedReader()
fun readLine(): String? = cin.readLine()
fun readLn() = cin.readLine()!!
@JvmField var _tokenizer: StringTokenizer = StringTokenizer("")
fun read(): String {
    while (_tokenizer.hasMoreTokens().not()) _tokenizer = StringTokenizer(cin.readLine() ?: return "", " ")
    return _tokenizer.nextToken()
}
fun readInt() = read().toInt()
fun readDouble() = read().toDouble()
fun readLong() = read().toLong()
fun readStrings(n: Int) = List(n) { read() }
fun readLines(n: Int) = List(n) { readLn() }
fun readInts(n: Int) = List(n) { read().toInt() }
fun readIntArray(n: Int) = IntArray(n) { read().toInt() }
fun readDoubles(n: Int) = List(n) { read().toDouble() }
fun readDoubleArray(n: Int) = DoubleArray(n) { read().toDouble() }
fun readLongs(n: Int) = List(n) { read().toLong() }
fun readLongArray(n: Int) = LongArray(n) { read().toLong() }
@JvmField val cout = PrintWriter(OUTPUT, false)

fun main(args: Array<String>) {
    val t = read().toBigInteger()
    if(t <= 25.toBigInteger()){
        val tt = t.toInt()
        cout.println( when(tt) {
            4 -> 3
            6 -> 5
            in arrayOf(8, 9, 10, 15, 16, 22) -> 7
            12 -> 11
            14 -> 13
            20 -> 19
            21 -> 19
            24 -> 23
            25 -> 23
            else -> 8
        })
    }else {
        cout.println(if(t.subtract(8.toBigInteger()).isProbablePrime(100) && t.rem(8.toBigInteger()) == BigInteger.ONE) 14 else 8)
    }
    cout.flush()
}