def solve():
    import sys
    K = int(sys.stdin.readline())
    if K == 0:
        print(0.0)
        return
    
    size = K
    matrix = []
    for s in range(size):
        row = [0.0] * (size + 1)
        row[s] = 6.0  # Coefficient for dp[s]
        for d in range(1, 7):
            current_sum = s + d
            if current_sum == K:
                continue
            elif current_sum > K:
                row[0] -= 1.0
            else:
                x = current_sum
                row[x] -= 1.0
        row[size] = 6.0  # RHS is always 6
        matrix.append(row)
    
    n = len(matrix)
    for i in range(n):
        # Partial pivoting
        max_row = i
        for j in range(i, n):
            if abs(matrix[j][i]) > abs(matrix[max_row][i]):
                max_row = j
        matrix[i], matrix[max_row] = matrix[max_row], matrix[i]
        
        pivot = matrix[i][i]
        if pivot == 0:
            print(0.0)
            return
        
        # Normalize pivot row
        for j in range(i, n + 1):
            matrix[i][j] /= pivot
        
        # Eliminate other rows
        for j in range(n):
            if j != i:
                factor = matrix[j][i]
                for k in range(i, n + 1):
                    matrix[j][k] -= factor * matrix[i][k]
    
    solution = [row[n] for row in matrix]
    print("{0:.5f}".format(round(solution[0], 5)))

solve()