using System;
public static class nonef{
public static double exp(double x){
	if(x<0)return 1/exp(-x);
	if(x>4){double r=exp(x/4); return r*r*r*r;}
	if(x>2){double r=exp(x/2); return r*r;}
	Func<double,vector,vector> expeq=(t,y)=>new vector(y[0]);
	double a=0;
	vector ya=new vector(1.0);
	vector res=ode.rk23(expeq,a,ya,x,acc:1e-3,eps:1e-3);
	return res[0];
	}
}