import math
def meteor(n):
r= .09
m=7
b=1.5e-3
x=200.*1000.
v=-20.*1000.
H=7.6*1000.
g=9.8
t_max=-x/v*10.
dt=t_max/n
for i in range (n):
	dx=v*dt
	x=x+dt
	if x<0.:
	return v
	F=b*v**2*mat.exp(-x/H)-m*g
	a=F/m
	dv=a*dt
	v=v+dv
	return-999