The package for this problem was not updated by the problem writer or Codeforces administration after we've upgraded the judging servers. To adjust the time limit constraint, a solution execution time will be multiplied by 2. For example, if your solution works for 400 ms on judging servers, then the value 800 ms will be displayed and used to determine the verdict.

April Fools Day Contest 2013 |
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Finished |

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*special problem

graph matchings

implementation

trees

*1700

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C. WTF?

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard output

HAI

I HAS A TUX

GIMMEH TUX

I HAS A FOO ITS 0

I HAS A BAR ITS 0

I HAS A BAZ ITS 0

I HAS A QUZ ITS 1

TUX IS NOW A NUMBR

IM IN YR LOOP NERFIN YR TUX TIL BOTH SAEM TUX AN 0

I HAS A PUR

GIMMEH PUR

PUR IS NOW A NUMBR

FOO R SUM OF FOO AN PUR

BAR R SUM OF BAR AN 1

BOTH SAEM BIGGR OF PRODUKT OF FOO AN QUZ AN PRODUKT OF BAR BAZ AN PRODUKT OF FOO AN QUZ

O RLY?

YA RLY

BAZ R FOO

QUZ R BAR

OIC

IM OUTTA YR LOOP

BAZ IS NOW A NUMBAR

VISIBLE SMOOSH QUOSHUNT OF BAZ QUZ

KTHXBYE

Input

The input contains between 1 and 10 lines, *i*-th line contains an integer number *x*_{i} (0 ≤ *x*_{i} ≤ 9).

Output

Output a single real number. The answer is considered to be correct if its absolute or relative error does not exceed 10^{ - 4}.

Examples

Input

3

0

1

1

Output

0.666667

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