Code 3 bài đây em nhá

bài 1:
uses crt;
var i,t:integer;
begin
clrscr;
t:=0;
for i:=1 to 100 do t:=t+i;
write(t);
readln
end.
..............................................................
bài 2:
uses crt;
var i,t,n:integer;
begin
clrscr;
write('nhap n=');readln(n);
t:=0;
for i:=1 to n do t:=t+i;
write(t);
readln
....................................................
bài 3
uses crt;
var i,t,n:integer;
begin
clrscr;
write('nhap n=');readln(n);
t:=0;
for i:=1 to n do if i mod 2=1 then t:=t+i;
write(t);
readln
end.
end.