Как организовать перестановку строк, дабы избежать деления на ноль?

procedure iterration;
const e=0.001;
var i,j,k,t,n,p:integer;
sum1:real;
f:boolean;
a,c,z:array [1..10,1..10] of real;
s1,x,x0,d,b,q:array [1..10] of real;
begin
ClrScr;
repeat{$I-}
writeln('Input the number of equations');
readln(n);
{$I+}
until (IOResult=0);
if n=0 then begin
clrscr;
{$I-}
repeat writeln('Sorry,try again to input number');
readln(n);
{$I+}
until (IOResult=0)
or (n<>0);
end;
for i:=1 to n do begin
writeln('Equation:',i);
for j:=1 to n do
begin
repeat{$I-}
write('Input string A(',i,',',j,'):');
readln(a[i,j]);
{$I+}
until (IOResult=0);
end;
repeat{$I-}
write('Input element: B(',i,'):');
readln(b[i]);
{$I+}
until (IOResult=0);
end;
ClrScr;
for i:=1 to n do
for j:=1 to n do
begin
   if i=j then c[i,j]:=0
else c[i,j]:=-a[i,j]/a[i,i];
end;
for i:=1 to n do
d[i]:=b[i]/a[i,i];
for i:=1 to n do
begin
sum1:=0;
for j:=1 to n do
sum1:=sum1+c[i,j];
s1[i]:=sum1;
end;
sum1:=s1[1];
for i:=2 to n do
if s1[i]>sum1 then sum1:=s1[i];
if abs(sum1)<1 then begin
for i:=1 to n do
x0[i]:=d[i];
for i:=1 to n do
begin
x[i]:=0;
for j:=1 to n do
x[i]:=x[i]+c[i,j]*x0[j];
end;
for i:=1 to n do
x[i]:=x[i]+d[i];
begin
for i:=1 to n do
x0[i]:=x[i];
 
for i:=1 to n do
begin
x[i]:=0;
for j:=1 to n do
x[i]:=x[i]+c[i,j]*x0[j];
end;
for i:=1 to n do
x[i]:=x[i]+d[i];
t:=0;
for i:=1 to n do
if abs(x[i]-x0[i])<e then t:=t+1;
if t=n then writeln ('Answer:');
for i:=1 to n do
write (x[i]:2:2,' ');
writeln
end;
end;
readln;
end;
end.
end.