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

using ll = long long;

void solve(){
  int i, j;
  int n = 6;
  vector<int> ra = {1,1,1,0,0,1};
  int cnt = 1000000;
  ll moves = 0;
  vector<pair<int,int>> pos;
  for(int i = 0; i < n; i++){
    for(j = i+1; j < n; j++){
      pos.push_back({i,j});
    }
  }
  for(int t = 0; t < cnt; t++){
    mt19937 rng(t);
    vector<int> a = ra;
    while(!is_sorted(a.begin(), a.end())){
      pair<int,int> cur = pos[uniform_int_distribution<int>(0,pos.size()-1)(rng)];
      i = cur.first;
      j = cur.second;
      swap(a[i],a[j]);
      moves++;
    }
  }
  long double ans = moves/(long double)cnt;
  cout << ans;
}

int main(){
  solve();
  return 0;
}