How to generate nonzero x (i, j) values using loop function 1: pop_size?

let

c=[10 2 20 11
    12  7  9  20 
    4 14 16 18];
s=[15
    25
    10];
d=[5 15 15 15];
[m,n]=size(c);
pop_size=25
gen_iter=100
phi=1:12
for ii=1:pop_size
    randi_phi = randperm(length(phi))
    for count = 1 : length(phi)
        count
        k= randi_phi(count)
        i=[1+mod((k-1),m)]
        j=[1+mod((k-1),n)]
        x(i,j)=min(s(i),d(j))
        s(i)= s(i)-x(i,j)
        d(j)= d(j)-x(i,j)
    end
end

I want to find x (i, j) until the loop pop_size = 25 but my math lab code results in x (i, j) = (m, n) = 0, even though if the loop uses length phi the value x (i, j) comes out or not zero. if anyone can help my mathlab code this. ? This I use a new genetic algorithm at the chromosome initialization stage