program oken; uses crt; var i,n,sum:longint; begin clrscr; write('nhap so n: '); readln(n); sum:=0; for i:=1 to n do sum:=sum+i; writeln('Tong=',sum); readln; end.
Sử dụng while... do:
program oken; uses crt; var i,n,sum:longint; begin clrscr; write('nhap so n: '); readln(n); sum:=0; i:=1; while i<=n do begin sum:=sum+i; i:=i+1; end; writeln('Tong=',sum); readln; end.
