# Survey Analysis

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#
#   WebEngage empowers companies to collect feedback and gather insights from visitors using survey and notifications.
#   An e-commerce company used the WebEngage customer engagement tool to ask visitors
#   if they want to buy the selected products at discounted prices. If the visitor said 'Yes', the product was
#   delivered to the customer at the discounted price. They collected the response for a whole week from Monday
#   to Sunday. Now they want to analyse which day most of the people said 'Yes' compared to other days.
#   For this, they want to calculate the standard deviation of the 'Yes' count on each day. Using the standard
#   deviation, we have a standard way of knowing which day was extra good, which day was extra bad,
#   and which day was just plain normal in terms of business.
#
#   Input format
#   The input contains 7 lines, depicting Monday to Sunday. Each line contains a string of 1 & 0. 1 means
#   the visitor said 'Yes', and 0 means the visitor said 'No'.
#
#   Output format
#   Output a single line with the result rounded to 4 decimal places,
#   which is the standarddeviation of the 'Yes' count on each day.
#
#   Input constraint
#   Number of visitors everyday doesn't exceed 1 million.
#
#   SAMPLE INPUT
#   11011
#   1010000
#   0010
#   1101
#   010
#   101111
#   001110
#
#   SAMPLE OUTPUT
#   1.3851
#
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