package main

import (
    "fmt"
    "math/rand"
    "time"
)



func main() {
    var NUM, taro, jiro, taro_win int
    NUM = 1000000
    taro_win = 0
    var N, K int
    fmt.Scan(&N, &K)
    NUM = NUM + 0
    var i, j, k, l int
    rand.Seed( time.Now().UnixNano())
    for i=0; i<NUM; i++ {
        taro = 0
        jiro = 0
        for j=0; j<N; j++ {
            jiro += rand.Intn(6) + 1
        }
        for k=0; k<K; k++ {
            taro += rand.Intn(3)+4
        }
        for l=0; l<N-K; l++ {
            taro += rand.Intn(6) + 1
        }
        if taro > jiro {
            taro_win += 1
        }
    }
    fmt.Printf("%f", float64(taro_win)/float64(NUM))
}