1/

uses crt;
var n:integer;
function TongChan(n:integer):integer;
var j:integer;
begin
   for j:=1 to n do if j mod 2 = 0 then TongChan:=TongChan+j;
end;
begin
   clrscr;
   write('Nhap n: '); readln(n);
   write('Tong cac so chan la: ',TongChan(n));
   readln
end.

2/

uses crt;
var n:integer;
function TongLe(n:integer):integer;
var j:integer;
begin
   for j:=1 to n do if j mod 2 <> 0 then TongChan:=TongChan+j;
end;
begin
   clrscr;
   write('Nhap n: '); readln(n);
   write('Tong cac so le la: ',TongLe(n));
   readln
end.

3/

uses crt;
var a,b:integer;
function max2so(a,b:integer):integer;
var max:integer;
begin
   if a>b then max:=a else max:=b;
   max2so:=max;
end;
begin
   clrscr;
   write('Nhap a: '); readln(a);
   write('Nhap b: '); readln(b);
   write('So lon hon la: ',max2so(a,b));
   readln
end.

4/

uses crt;
var a,b:integer;
function main(a,b:integer):integer;
var min2so:integer;
begin
   if a>b then min:=b else min:=a;
   min2so:=min;
end;
begin
   clrscr;
   write('Nhap a: '); readln(a);
   write('Nhap b: '); readln(b);
   write('So nho hon la: ',min2so(a,b));
   readln
end.