#include <bits/stdc++.h>
using namespace std;
int b_row, b_col, memo[16][3][3];
char b[2];
bool rangeCheck(int row, int col) {
  if (row >= 0 && row <= 2 && col >= 0 && col <= 2)
    return true;
  else {
    return false;
  }
}
int translate(char ch) {
  switch (ch) {
    case 'A':
      return 0;
    case 'B':
      return 1;
    case 'C':
      return 2;
    case 'D':
      return 10;
    case 'E':
      return 11;
    case 'F':
      return 12;
    case 'G':
      return 20;
    case 'H':
      return 21;
    case 'I':
      return 22;
  }
  return -1;
}
int main() {
  int n, tmp, energy_row, energy_col, row, col, div_row[4] = {-1, 0, 0, 1},
                                                div_col[4] = {0, -1, 1, 0};
  char start[2], energy[2];
  while (true) {
    scanf("%d", &n);
    if (n == 0) break;
    for (int i = 0; i < 16; i++) {
      for (int p = 0; p < 3; p++) {
        for (int k = 0; k < 3; k++) memo[i][p][k] = 0;
      }
    }
    scanf("%s %s %s", start, energy, b);
    tmp = translate(b[0]);
    b_row = tmp / 10;
    b_col = tmp % 10;
    tmp = translate(energy[0]);
    energy_row = tmp / 10;
    energy_col = tmp % 10;
    tmp = translate(start[0]);
    row = tmp / 10, col = tmp % 10;
    memo[0][row][col] = 1;
    for (int loop = 0; loop <= n - 1; loop++) {
      for (int i = 0; i < 3; i++) {
        for (int k = 0; k < 3; k++) {
          if (i != b_row || k != b_col) {
            for (int p = 0; p < 4; p++) {
              if (rangeCheck(i + div_row[p], k + div_col[p]) == true &&
                  (i + div_row[p] != b_row || k + div_col[p] != b_col)) {
                memo[loop + 1][i + div_row[p]][k + div_col[p]] +=
                    memo[loop][i][k];
              } else {
                memo[loop + 1][i][k] = memo[loop][i][k];
              }
            }
          }
        }
      }
    }
    printf("%.8lf\n",
           ((double)memo[n][energy_row][energy_col]) / ((double)pow(4, n)));
  }
  return 0;
}
