#include <iostream>


double compute_pi( const int PRECISION )
{
	double pi = 4.0;
	for( int i = 0; i < PRECISION; ++i )
	{
			pi += (i % 2 == 0 ? -4.0 : 4.0) / ( 3.0 + i * 2 );
	}
	return( pi );
}

int main() {
	std::cout << compute_pi( 1e6 ) << std::endl;
	return 0;
}