unittest
{
	assert( [ "3" ].parse.expand.solve == 2 );
	assert( [ "6" ].parse.expand.solve == 9 );
	assert( [ "11" ].parse.expand.solve == 30 );
	assert( [ "50" ].parse.expand.solve == 625 );
}



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

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

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

auto solve( long k )
{
	auto odd = k / 2 + ( k % 2 == 1 );
	auto even = k / 2;
	
	return odd * even;
}
