Tin học [lớp 9] lập trình

uses crt;
var a,b,c:array[1..100] of integer;
n,i,m,j,k:integer;
begin
    clrscr;
    repeat
        write('Nhap n:');readln(n);
        if (n<1) or (n>20) then writeln('Nhap lai');
    until (n>=1) and (n<=20);
    repeat
        write('Nhap m:');readln(m);
        if (m<1) or (m>20) then writeln('Nhap lai');
    until (m>=1) and (m<=20);
    for i:=1 to n do
        begin
            write('a[',i,']:');readln(a[i]);c[i]:=a[i];
        end;
    for i:=1 to m do
        begin
            write('b[',i,']:');readln(b[i]);
        end;
    for i:=1 to n-1 do
    for j:=2 to n do
    if (i<j) and(a[i]>a[j]) then
    begin
        k := a[i];
        a[i]:=a[j];
        a[j]:=k;
    end;
    for i:=1 to m-1 do
    for j:=2 to m do
    if (i<j) and(b[i]>b[j]) then
    begin
        k := b[i];
        b[i]:=b[j];
        b[j]:=k;
    end;
    writeln('Mang A sau khi sap xep:');
    for i := 1 to n do write(a[i]:6);writeln;
    writeln('Mang B sau khi sap xep:');
    for i := 1 to m do write(b[i]:6);writeln;
    for i := n+1 to m+n do c[i]:=b[i-n];
    for i:=1 to m+n-1 do
    for j:=2 to n+m do
    if (i<j) and(c[i]>c[j]) then
    begin
        k := c[i];
        c[i]:=c[j];
        c[j]:=k;
    end;
    writeln('Mang C:');
    for i := 1 to m+n do write(c[i]:6);
readln
end.