Var
a, b: longint;
begin
a := 1;
for b := 1 to 20 do
if (b mod 2 = 1) then
a := a * b;
writeln(a);
end.
--------------------
var
b: integer;
begin
for b := 20 to 50 do
if (b mod 2 = 0) then
writeln(b);
end.
------------------
var
a, b: integer;
begin
a := 1;
for b := 1 to 10 do
a := a * b;
writeln(a);
end.
----------------------
var
a, b: integer;
begin
for b := 2 to 48 do
if (b mod 2 = 0) then
a := a + b;
writeln(a);
end.
------------------------
var
i, k: integer;
begin
readln(i);
k := i div 1000;
i := i mod 1000;
i := ((i + 1000 * (i mod 10)) div 10) * 10 + k;
writeln(i);
end.
--------------------------
Это с первого по... какое-то там:)