  The great progress made recently in the sector of Flavor Physics has enabled
to establish CP violation in the B-meson decays. The unitarity triangle derived
from the unitarity relation $V_{ub}^* V_{ud} + V_{cb}^* V_{cd} + V_{tb}^*
V_{td} = 0$ has been measured very precisely. To further asses our
understanding of CP violation, it would be useful to carry out similar
measurement of other triangles. In this note, we investigate the triangle
derived from the relation $V_{ub}^* V_{us} + V_{cb}^* V_{cs} + V_{tb}^* V_{ts}
= 0$. Two angles of this triangle ($\alpha_s$ and $\beta_s$) could be measured
very accurately at FCCee using the decays $B_s(\overline{B_s})\rightarrow
D^\pm_sK^\mp$ and $B_s(\overline{B_s})\rightarrow J/\psi \phi$ respectively, as
discussed elsewhere by us. This note concentrates on the measurement of the
third angle $\gamma_s$ using the modes $B^\pm \to \overline{D^0}(D^0)K^\pm$. We
show that a direct measurement of the angle $\gamma_s$ is possible with some
specific $B^\pm$ decays with an estimated resolution of the order of 1$^\circ$.
