CVX optimization for 2 dimensions variables

Dear All,
I have written my code :
n=10
m=20
L_tot=[1:1:10];
cvx_begin
variable f(n,m); % two dimensional matrix
variable L(n,m); % two dimensional matrix
dual variables A B C D E F
minimize (sum(f.^2)+sum(power(2,2.L/200)));
subject to
A: sum(L)-L_tot==0;
B: -L<=0;
C: -R<=0;
D: f-1000<= 0;
E: L<=2
f ;
F: 2*L-R<=0;
cvx_end
but, Unfortunately, I am unable to solve the problem and this problem exist:

“Your objective function is not a scalar.”

but, the results seems scalar!!!

If possible, please help me how to resolve the problem.

Thanks all.