Physics: Harmonics Help?

You d a string over a pulley and hang a m of 35.0 kg from one end. You tie the other end to a point a distance L from the pulley so that the string is horizontal between this point and the pulley. The string has a linear m density of 0.0470 kg/m. If you want the difference in frequency between any two consecutive harmonics to be 35.0 Hz, what will the distance L have to be?