For - do:
Program BTT;
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('Tong la: ',s);
Readln
End.
While - do:
Program BTT;
Uses crt;
Var n,i,s: longint;
Begin
Clrscr;
Write('Nhap n: '); Readln(n);
s:=0; i:=1;
While i<=n do
Begin
s:=s+i;
inc(i);
End;
Write('Tong la: ',s);
Readln
End.