Bài 1:

Program FNG;
Uses crt;
Var n,i,s: longint;
Begin
        Clrscr;
        Write('Nhap n: '); Readln(n);
        s:=0;
        For i:=1 to n do
                s:=s+i;
        Write('S = ',s);
        Readln
End.

Bài 2:

Program FNG;
Uses crt;
Var A: array[1..1000] of longint;
    n,i,s: longint;
Begin
        Clrscr;
        Write('Nhap n: '); Readln(n);
        For i:=1 to n do
        Begin
                Write('A[',i,'] = ');
                Readln(A[i]);
        End;

        s:=0;
        For i:=1 to n do
                s:=s+A[i];

        Writeln('S = ',s);

        For i:=1 to n do
                Write(A[i],' ');
        Readln
End.

BT1:

program Tin_hoc;

uses crt;

var i,tong,n:integer;

begin

clrscr;

write('Nhap n: ');readln(n);

tong:=0;

for i := 1 to n do tong:= tong + i;

writeln('Tong = ',tong);

readln;

end.

BT2:

program Tin_hoc;

uses crt;

var i,n,tong:integer;

      a: array [1..100000] of integer;

begin

clrscr;

write('Nhap n: ');readln(n);

tong:=0;

writeln('Nhap ',n,' phan tu:');

for i:= 1 to n do

  begin

  write('a[',i,'}: ');

  readln(a[i]);

  tong:= tong+a[i]

  end;

writeln('Tong cua ',n,' phan tu la: ',tong);

readln;

end.