subroutine mysub(permno,comp,ret,begret,endret,mkt)
real ret(7000),mkt(7000)
integer permno,begret,endret
character*32 comp
x=0; y=0; x2=0; y2=0; xy=0
t=0
do i = begret,endret {
	if(ret(i) >= -1) {
		if( i > begret) {
			if( ret(i-1) >= -1) {
				t=t+1
				x = x + mkt(i)
				y = y + ret(i)
				x2 = x2 + mkt(i) * mkt(i)
				y2 = y2 + ret(i) * ret(i)
				xy = xy + mkt(i) * ret(i)
				}
			}
		}
	}
if(t > 0 ) {
x = x/t
y = y/t
x2 = x2 - t*x*x
xy = xy - t*x*y
beta = xy/x2
} else { 
beta = -999999 }
write(6,*)permno," ",comp,beta
end