#include <bits/stdc++.h>
using namespace std;

const int N = 624;
const int M = 397;
const unsigned int MATRIX_A = 0x9908b0dfU;
const unsigned int UPPER_MASK = 0x80000000U;
const unsigned int LOWER_MASK = 0x7fffffffU;

vector<unsigned int> mt;
int mti = N + 1;

void init_genrand(unsigned int s) {
    mt.push_back(s & 0xffffffffU);
    for(mti=1; mti<N; mti++) {
        mt.push_back(1812433253U * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
        mt[mti] &= 0xffffffffU;
    }
}

void init_by_array(vector<unsigned int> init_key) {
    int key_length = init_key.size();
    init_genrand(19650218U);
    int i = 1, j = 0;
    int k = N > key_length ? N : key_length;
    for( ; k; k--) {
        mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525U)) + init_key[j] + j;
        mt[i] &= 0xffffffffU;
        i++; j++;
        if(i >= N) { mt[0] = mt[N-1]; i = 1; }
        if(j >= key_length) { j = 0; }
    }
    for(k=N-1; k; k--) {
        mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941U)) - i;
        mt[i] &= 0xffffffffU;
        i++;
        if(i >= N) { mt[0] = mt[N-1]; i = 1; }
    }
    mt[0] = 0x80000000U;
}

unsigned int genrand_int32(void) {
    unsigned int y;
    static unsigned int mag01[2] = {0x0U, MATRIX_A};
    if(mti >= N) {
        if(mti == N + 1) { init_genrand(5489U); }
        int kk;
        for(kk=0; kk<N-M; kk++) {
            y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
            mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1U];
        }
        for(; kk<N-1; kk++) {
            y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
            mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1U];
        }
        y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
        mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1U];
        mti = 0;
    }
    y = mt[mti++];
    y ^= (y >> 11);
    y ^= (y << 7) & 0x9d2c5680U;
    y ^= (y << 15) & 0xefc60000U;
    y ^= (y >> 18);
    return y;
}

int genrand_int31(void) {
    return (int)(genrand_int32() >> 1);
}

int main(void) {
    clock_t start = clock();
    time_t seed = time(0);
    vector<unsigned int> init;
    init.push_back(0x123);
    init.push_back(0x234);
    init.push_back(0x345);
    init.push_back(0x456);
    init.push_back(seed);
    init_by_array(init);

    int n, k;
    int turn, win;
    scanf("%d%d", &n, &k);
    for(turn=1, win=0; ; turn++) {
        int taro = 0, jiro = 0;
        for(int i=0; i<n-k; i++) {
            taro += genrand_int31() % 6 + 1;
            jiro += genrand_int31() % 6 + 1;
        }
        for(int i=n-k; i<n; i++) {
            taro += genrand_int31() % 3 + 4;
            jiro += genrand_int31() % 6 + 1;
        }
        if(taro > jiro) { win++; }
        clock_t now = clock();
        if((now - start) / CLOCKS_PER_SEC >= 4) {
            break;
        }
    }
    printf("%f\n", win * 1. / turn);
    return 0;
}