Let z1 (i = 1, 2, 3, 4) represent the vertices of a square all of which lie on the sides of the triangle with vertices (0, 0), (2, 1) and (3, 0). If z1 and z2 are purely real, then area of triangle formed by z3, z4 and origin is m (where m and n are in their lowest form). Find the value of (m + n).