program main
    implicit none
    
    integer :: n
    integer :: m
    
    integer :: i, j
    
    double precision :: p
    
    double precision :: expected_trees
    
    read *, n, m
    read *, p
    
    if (n == 1) then
        expected_trees = merge(p, dble(m-2) * p**3 + 2.0d0 * p**2, m == 1)
    else
        expected_trees = merge(                                                       &
            dble(n-2) * p**3 + 2.0d0 * p**2,                                          &
            dble(n-2) * dble(m-2) * p**5 + dble(2*n + 2*m - 8) * p**4 + 4.0d0 * p**3, &
            m == 1                                                                    &
        )
    end if
    print *, expected_trees
end program main