//no-unlocked

int n;
double x[310], y[310], z[310];

{
	rd(n);
	rd((x, y, z)(n + 1));
	double s;
	rep(i, 1, n + 1) rep(j, i + 1, n + 1) rep(k, j + 1, n + 1) {
		double p=(y[j]-y[i])*(z[k]-z[i])-(z[j]-z[i])*(y[k]-y[i]);
		double q=(z[j]-z[i])*(x[k]-x[i])-(x[j]-x[i])*(z[k]-z[i]);
		double r=(x[j]-x[i])*(y[k]-y[i])-(y[j]-y[i])*(x[k]-x[i]);
		s+=fabs(p*(x[0]-x[i])+q*(y[0]-y[i])+r*(z[0]-z[i]))/sqrt(p*p+q*q+r*r);
	}
	wt(s);
}