program main
implicit none
real::n,y,t,v
real,parameter::a=6900,m=4*10**5
open(10,file="test.txt")
v=2
n=(m/a**3)**0.5
t=(y/3*v)
50 y=(1/n)*(4*sin(n*t)-3*n*t)*v
if(y==12043) then
write(10,100)t
write(*,100)t
else
if(y>12043) then
t=t+1.27
goto 50
else
if(y<12043) then
t=t-0.52
goto 50
endif
endif
endif
100 format("t=",f8.2)
end