#include <bits/stdc++.h>   using namespace std;   namespace jenga {   inline char get_unempty_char() {     char ch;     while (isspace(ch = getchar()))       ;     return ch;   }   const double eps(1e-10), Inf = 1e+64;   const int RED = 1, BLUE = 2, GREEN = 3, EMPTY = 0, N = 6, Base = 67,             mod = 3000007;   int n, last[mod] = {}, next[mod] = {}, total_edge = 0, s[N * 3 - 1] = {},          tot = 0;   unsigned long long hv[mod] = {};   double f[mod] = {};   inline void add(unsigned long long hash, double v) {     int u = hash % mod;     next[++total_edge] = last[u];     last[u] = total_edge;     f[total_edge] = v;     hv[total_edge] = hash;   }   inline int get_num(char ch) {     if (ch ==  R ) return RED;     if (ch ==  B ) return BLUE;     if (ch ==  G ) return GREEN;     if (ch ==  E ) return EMPTY;     assert(false);   }   void init() {     n = get_unempty_char() -  0 ;     for (int i = 1; i <= n; ++i) {       s[i] |= get_num(get_unempty_char()) << 0;       s[i] |= get_num(get_unempty_char()) << 2;       s[i] |= get_num(get_unempty_char()) << 4;     }     tot = n;   }   inline unsigned long long hash(int *s, int k, int up) {     static int v[N * 3 + 10] = {};     unsigned long long h = 0;     int tot = 0;     for (int i = 1; i <= k; ++i) {       int c1 = (s[i] >> 4) & 3, c2 = (s[i]) & 3, c3 = (s[i] >> 2) & 3;       v[++tot] =           c1 > c2 ? (c3 << 2) | c1 | (c2 << 4) : (c3 << 2) | c2 | (c1 << 4);     }     sort(v + 1, v + tot + 1);     int c1 = (up >> 4) & 3, c2 = up & 3, c3 = (up >> 2) & 3;     if (c1 > c2) up = c1 | (c2 << 4) | (c3 << 2);     for (int i = 1; i <= tot; ++i) h = h * Base + v[i];     h = h * Base + up;     return h;   }   double work(int *s, int tot, int up) {     unsigned long long h = hash(s, tot, up);     for (int i = last[h % mod]; i; i = next[i])       if (hv[i] == h) return f[i];     double v[4] = {Inf, Inf, Inf, Inf};     int to = tot, D = 6;     if ((up & 3) && ((up >> 2) & 3) && ((up >> 4) & 3)) s[++to] = up, up = 0;     for (int i = 1; i <= tot; ++i) {       int c1 = s[i] & 3, c2 = (s[i] >> 2) & 3, c3 = (s[i] >> 4) & 3, ns = s[i];       if (c1 && c2 && c3 && v[c2] > eps) {         s[i] = 0;         if (!(up & 3))           v[c2] = min(v[c2], work(s, to, up | c2));         else if (!(up >> 4 & 3))           v[c2] = min(v[c2], work(s, to, up | c2 << 4));         if (!(up >> 2 & 3)) v[c2] = min(v[c2], work(s, to, up | c2 << 2));         s[i] = ns;       }       if (c1 && c2 && v[c1] > eps) {         s[i] = c3 == 0 ? 0 : s[i] & ~3;         if (!(up & 3))           v[c1] = min(v[c1], work(s, to, up | c1));         else if (!(up >> 4 & 3))           v[c1] = min(v[c1], work(s, to, up | c1 << 4));         if (!(up >> 2 & 3)) v[c1] = min(v[c1], work(s, to, up | c1 << 2));         s[i] = ns;       }       if (c2 && c3 && v[c3] > eps) {         s[i] = c1 == 0 ? 0 : s[i] & ~48;         if (!(up & 3))           v[c3] = min(v[c3], work(s, to, up | c3));         else if (!(up >> 4 & 3))           v[c3] = min(v[c3], work(s, to, up | c3 << 4));         if (!(up >> 2 & 3)) v[c3] = min(v[c3], work(s, to, up | c3 << 2));         s[i] = ns;       }     }     double sum = 0;     if (v[1] != Inf) sum += v[1], D -= 1;     if (v[2] != Inf) sum += v[2] * 2, D -= 2;     if (v[3] != Inf) sum += v[3] * 2, D -= 2;     sum = D == 6 ? 0 : (sum + 6) / (6 - D);     add(h, sum);     return sum;   }   int Main() {     init();     printf( %.15f n , work(s, tot - 1, s[tot]));     return 0;   }   }  // namespace jenga   int main() {     jenga::Main();     return 0;   }