#include <vector>
#include <random>
#include <cstdio>
#include <ctime>
#include <unistd.h>
using namespace std;

int main(){
    int N,K;
    scanf("%d%d",&N,&K);
    int T=2000000;
    int S=0;
    uniform_int_distribution<int> gooddice(1,6);
    uniform_int_distribution<int> badddice(4,6);
    mt19937_64 engine(0);
    for(int I=0;I<T;I++){
        int a=0,b=0,i=0;
        for(;i<K;i++)a+=gooddice(engine),b+=badddice(engine);
        for(;i<N;i++)a+=gooddice(engine),b+=gooddice(engine);
        if(a<b)S++;
    }
    printf("%f\n",S*1.0/T);
}