While...do
program bai1;
uses crt;
var n,S,i:integer;
begin
clrscr;
write(' n = '); readln(n);
S:=0; i:=1;
while i<=n do
begin
S:=S+i;
i:=i+1;
end;
write('Tong la: ', S);
readln;
end.
For...do
program bai 2;
uses crt;
var n,S,i:integer;
begin
clrscr;
write(' n = '); readln(n) ;S:=0;
for i:=1 to n do S:=S+i;
write('Tong la: ', S);
readln;
end.