program BT;
uses crt;
var n,d: integer;
i,S,T: longint;
Begin
clrscr;
write('Nhap n: '); readln(n);
for i:=1 to n do
begin
S:=S+i;
if i mod 5=0 then d:=d+1;
if (i mod 3=0) and (i mod 5=0) then T:=T+i;
end;
writeln('a) S = ',S);
writeln('b) Tu 1 den ',n,' co ',d,' so chia het cho 5');
write('c) Tong cac so chia het cho 3 va 5 = ',T);
readln
End.