import java.util.Scanner

fun main() {
    val sc = Scanner(System.`in`)
    var a = Array<Int>(9) { 0 }
    var n = sc.nextInt()
    while (n > 0) {
        if (n % 10 == 9) a[6]++
        else a[n % 10]++
        n /= 10
    }
    a[6] = (a[6] + 1) / 2
    a.sortDescending()
    print(a[0])
}