Submission #1519775

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Source Code Expand

import std.array;
import std.stdio;
import std.range;
import std.algorithm;
import std.format;
import std.bigint;
import std.functional;
import std.string;
import std.conv;

void main()
{
	long N = readln.chomp.to!long();
	long[] C = iota(N).map!(_ => readln.chomp.to!long).array();
	format("%07f", solve(C)).writeln();
}

double solve(long[] C)
{
	double p = iota(1, C.length + 1).reduce!((a, b) => a * b).to!double;
	long[long] divisor;
	double result = 0;
	C.sort().reverse();
	foreach (i, c; C)
	{
		if (c in divisor)
			continue;
		divisor[c] = 0;
		foreach (d; C[i .. $])
			if (c % d == 0)
				divisor[c]++;
	}
    
	foreach (c; C)
	{
		if (divisor[c] % 2 == 0)
		{
			result += 1.0 / 2;
		}
		else
		{
			result += cast(double)(divisor[c] + 1) / (2 * divisor[c]);
		}

	}
	return result;
}

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