poorly explaind Matlab error

function[x,ss,n]=c3jacobi(N,a,x0,eps,maxit)

if nargin<5, maxit=100;end

if nargin<4, eps=1.0E-6;end;

if nargin<3, error('at least 3 nargin');end;

n=0;

for l=1:maxit

n=n+1;

for k=1:N

sum=0;

for j=1:N

if j~=k, sum=sum+a(k,j)*x0(j);end;

end;

x(k)=(a(k,N+1)-sum)/a(k,k);

end;

ss=0;

for k=1:N

if abs(x(k)-x0(k))>ss

ss=abs(x(k)-x0(k));

end;

end;

if ss<eps,break;end;

for k=1:N,x0(k)=x(k);end;

end;

But when I press F5 button to run, the Mathlab appeared this error : ??? Error using ==> c3jacobi at 4

Please help me(Clapping)