Disciplined convex programming error

    Hello all,
    I have a problem with my code.
    I have a variables: 
    variable Por(1,3);
     and some other variables which finally has been used in a function and made a vector with size of 24, "u" (where u(x1,..xn)=A*x1+...Z*xn))
    so we have:
    u   : CVX real affine expression (24x1 vector)
    Por : CVX real affine expression (1x3 vector)
    y   : a costant vector (3x24 matrix)
    my function in CVX is:
    Min (Por*y*u)

why this line (Min (Por*y*u)) cause this error?

    ??? Error using ==> cvx.mtimes at 152
    Disciplined convex programming error:
        Cannot perform the operation {affine}*{mixed convex/constant}

hat should I do to solve that?

Your problem is very likely nonconvex, and CVX cannot solve it.