How can I fix a solve error?

I've done a program but I can't execute it because I keep getting this error:

??? Error using ==> char
Complex values cannot be converted to chars

Error in ==> sym.solve at 46
    S{k} = char(varargin{k});

Error in ==> foro at 24
        cf(i,j)=solve(PRe,c);

I need some help to fix the problem. Here is the program:

clear all
close all

s=input('Introduce s (1-40): ');
n=input('Introduce n (1-100): ');
af=zeros(1,s);
bf=zeros(s,n);
cf=zeros(s,n);
B=zeros(1,s); 
C=zeros(1,s);

syms a b c;
F=6*a^3-10*b^2+c+i*(2*a+b+c);
Re=real(F)      
Im=imag(F)     

for i=1:s
    af(i)=i;
    a=af(i);
    for j=1:n
        bf(i,j)=j;
        b=bf(i,j);
        PRe(i,j)=subs(Re);      
        cf(i,j)=solve(PRe,c);
        c=cf(i,j);
        PImag(i,j)=subs(Im);        
        if PImag(i,j)==0
            B(1,i)=bf(i,j);
            C(1,i)=cf(i,j);
            break;
        else
           bf(i,j)=bf(i,j);
        end
        j=j+1;
    end
    i=i+1;
end

disp('B is: ' )
B

Thank you!

[Thomas Koelen]

I can't help you right now, all the symbolic toolboc auths are in use at my work at the moment, but what I can tell you is:

Don't use i as your start variable because it overwrites matlabs i,

don't do this: i=i+1; and j=j+1 you are using a for loop, your loop adds 1 every iteration by default.

[Lorena Ortiz]

Hi Thomas, I tried what you said but still gives me the same error..

Thank you anyway!