Program tinh_tong;
Var i,n,s:integer;
Begin
S:=0;
Write('nhap n =');readln(n);
For i:= 1 to n do s:= s+i;
Write('tong',n,'so tu nhien dau tien = ',s);
Readln
End.
minh khong biet co dung khong nhung co gang lam bai that tot nhe chuc ban may man