G. On a plane
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Input

The first line contains a single integer n (1 ≤ n ≤ 1000) — the number of points on a plane.

Each of the next n lines contains two real coordinates xi and yi of the point, specified with exactly 2 fractional digits. All coordinates are between  - 1000 and 1000, inclusive.

Output

Output a single real number θ — the answer to the problem statement. The absolute or relative error of your answer should be at most 10 - 2.

Examples
Input
8-2.14 2.06-1.14 2.04-2.16 1.46-2.14 0.70-1.42 0.40-0.94 -0.48-1.42 -1.28-2.16 -1.62
Output
5.410
Input
52.26 1.442.28 0.642.30 -0.301.58 0.663.24 0.66
Output
5.620
Input
86.98 2.066.40 1.125.98 0.245.54 -0.607.16 0.307.82 1.248.34 0.248.74 -0.76
Output
5.480
Input
510.44 2.0610.90 0.8011.48 -0.4812.06 0.7612.54 2.06
Output
6.040
Input
816.94 2.4215.72 2.3814.82 1.5814.88 0.5015.76 -0.1616.86 -0.2017.00 0.8816.40 0.92
Output
6.040
Input
720.62 3.0021.06 2.2821.56 1.3621.66 0.5621.64 -0.5222.14 2.3222.62 3.04
Output
6.720