program tinhtong;
uses crt;
var n,i:integer;
S:longint;
begin
write('nhap so n='); readln(n);
S:=0
for i:=1 to n do S:=S+i;
writeln('tong S la,S,');
readln
end.
program Tinh_tong;
Var n: integer;
s: longint;
BEGIN
repeat
write( 'Nhap n: '); readln(n);
until (n>=0);
s:=0;
for i:=1 to n do
s:=s+i;
write('Tong cac so tu 1 toi ', n,' =', s);
readln
END.
var n,i,s:integer;
begin
write('n=');readln(n);
s:=0;
for i:=1 to n do s:=s+i;
writeln(' tong la 's);
readln;
end.