use proconio::*;
fn main(){
    input!{ n: usize, k: usize}
    let mut dp1 = vec![vec![0.; 6*n+1]; n+1];
    dp1[0][0]=1.;
    for i in 0..n{
        for j in 0..=6*i{
            for k in 1..=6{
                dp1[i+1][j+k]+=dp1[i][j]/6.;
            }
        }
    }
    let mut dp2= vec![vec![0_f64; 6*n+1]; n+1];
    dp2[0][0]=1.;
    for i in 0..k{
        for j in 0..=6*i{
            for k in 4..=6{
                dp2[i+1][j+k]+=dp2[i][j]/3.;
            }
        }
    }
    for i in k..n{
        for j in 0..=6*i{
            for k in 1..=6{
                dp2[i+1][j+k]+=dp2[i][j]/6.;
            }
        }
    }
    let mut ans=0.;
    for i in 0..=6*n{
        for j in i+1..=6*n{
            ans+=dp1[n][i]*dp2[n][j];
        }
    }
    println!("{:.10}", ans);
}