Заполнение матрицы по правилу

const c=5;
var memory,i,j,g,p:integer; mas:array[1..5,1..5] of integer; 
 
begin
g:=1;j:=1;i:=1;
while p<(c-1) do begin
 
for j:=j to c-p do begin
mas[i,j]:=g;
inc(g);
end;
g:=g-1;
 
for i:=i to c-p do begin
mas[i,j]:=g;
inc(g);
end;
g:=g-1;
 
for j:=j downto p+1 do begin
mas[i,j]:=g;
inc(g);
end;
inc(p);
g:=g-1;
 
for i:=i downto p+1 do begin
mas[i,j]:=g;
inc(g);
end;
g:=g-1;
end;
 
for i:=1 to c do begin
for j:=1 to c do begin
write(mas[i,j]:3);
end;
writeln;
end;
end.

uses crt;
const nmax=20;
var a:array[1..nmax,1..nmax] of integer;
    m,n,i,j,k,z:integer;
begin
clrscr;
repeat
write('Количество строк до ',nmax,' m=');
read(m);
until m in [1..nmax];
repeat
write('Количество столбцов до ',nmax,' n=');
read(n);
until n in [1..nmax];
writeln('Исходная матрица:');
for j:=1 to n do
 begin
  inc(k);
  a[1,j]:=k
 end;
for i:=2 to m do
 begin
  inc(k);
  a[i,n]:=k
 end;
for i:=m downto 2 do
 begin
  inc(k);
  a[i,n-1]:=k
 end;
for j:=n-2 downto 1 do
 begin
  inc(k);
  a[2,j]:=k
 end;
for i:=3 to m do
if odd(i) then
for j:=1 to n-2 do
 begin
  inc(k);
  a[i,j]:=k
 end
else
for j:=n-2 downto 1 do
 begin
  inc(k);
  a[i,j]:=k
 end;
for i:=1 to m do
 begin
  for j:=1 to n do
  write(a[i,j]:3);
  writeln
 end;
end.