  We examine two-spin (2S) and cyclic four-spin (4S) magnetic interactions in
insulating ladder and two-dimensional (2D) cuprates. By a comparison of
eigenstates between d-p and Heisenberg models, we evaluate magnitudes of these
interactions. We find that the 4S interaction is $\sim$10% of nearest
neighboring 2S interaction, and a diagonal 2S interaction is considerably
small. The 4S interaction for a ladder cuprate is larger than that for 2D one,
and plays an important role in the low-energy excitation. The Heisenberg ladder
with the obtained 2S and 4S interactions reproduces very well the experimental
result of the temperature dependence of the magnetic susceptibility.
