#include <bits/stdc++.h> using namespace std; signed main(){ int N, K; cin >> N >> K; const int trial = ( int ) 1e7; int win_cnt = 0; for( int i = 0; i < trial; ++i ){ int nirou = 0; for( int j = 0; j < N; ++j ) nirou += rand() % 6 + 1; int tarou = 0; for( int j = 0; j < N - K; ++j ) tarou += rand() % 6 + 1; for( int j = 0; j < K; ++j ) tarou += rand() % 3 + 4; win_cnt += tarou > nirou; } cout << fixed << setprecision( 6 ) << 1.0 * win_cnt / trial << endl; return 0; }