unittest
{
	assert( [ "3" ].parse.expand.solve == "1.000000" );
	assert( [ "999" ].parse.expand.solve == "36926037.000000" );
}



import std.conv;
import std.format;
import std.range;
import std.stdio;
import std.typecons;

void main()
{
	stdin.byLineCopy.parse.expand.solve.writeln;
}

auto parse( Range )( Range input )
if( isInputRange!Range && is( ElementType!Range == string ) )
{
	auto l = input.front.to!( long );
	return tuple( l );
}

auto solve( long l )
{
	return format( "%0.6f", ( l / 3.0L ) ^^ 3 );
}
