c program to calculate semi-major axes
         real p,op,mstar
         print*,'Enter orbital period in days:'
         read*,p
         op=p*24.0*3600.0/3.14
         print*,'Enter radius of star (solar), and Rp(m):'
         read*,rs,rp
         r=rs*7.0e+08
         print*,'Enter transit length (hours):'
         read*,t
         tt=t*3600.0
         a=op*(rs+rp)/tt
         write(6,10)a
10       format(1x,'semi = ',es9.2)
         print*,'Enter mass of star (Msun):'
         read*,mstar
         zm=mstar*2.0e30
         zp=op*3.14
         g=6.67e-11
         spi=3.14**2
         aaa=zp**2*g*zm/4.0/spi
         write(6,10)aaa**0.333
          stop
           end