#include<cmath>
using namespace std;

#define NLAYERS_BCAL 10
double BCAL_tdiff(double geometric_mean, int layer)
{
	double tw_par[NLAYERS_BCAL][7] ={
		{-1.95554, -16.6392, 8.69029, -1.01706, -0.132453, 0.0341, -0.00181484},	// layer 1
		{787.024, -876.486, 400.552, -96.0572, 12.7504, -0.888752, 0.0254369},	// layer 2
		{-14.9728, 6.79441, -0.341158, -0.153762, 0.00173204, 0.00411765, -0.000306681},	// layer 3
		{3722.22, -4127.48, 1877.9, -449.199, 59.641, -4.17114, 0.120145},	// layer 4
		{0, 0, 0, 0, 0, 0, 0},	// layer 5
		{0, 0, 0, 0, 0, 0, 0},	// layer 6
		{0, 0, 0, 0, 0, 0, 0},	// layer 7
		{0, 0, 0, 0, 0, 0, 0},	// layer 8
		{0, 0, 0, 0, 0, 0, 0},	// layer 9
		{0, 0, 0, 0, 0, 0, 0}	// layer 10
		};

	layer = layer<1 ? 1:layer>NLAYERS_BCAL ? NLAYERS_BCAL:layer;
	double *p = tw_par[layer-1];
	double x = log(geometric_mean);
	return p[0]+x*(p[1]+x*(p[2]+x*(p[3]+x*(p[4]+x*(p[5]+x*p[6])))));
}