uses crt;

var i,n:integer;

      s:longint;

begin

write('nhap n:');readln(n);

for i:=1 to n do if i mod 2=0 then s:=s+i;

write('tong cac phan tu chan trong day la:',s);

readln;

end.

uses crt;

var n,i:integer;

      s:longint;

begin

clrscr;

writeln('nhap n:');readln(n);

s:=1;

for i:=1 to n do s:=s*i;

write('tich cua ',n,'so tu nhien dau tien la:',s);

readln;

end.

uses crt;

var n,i:integer;

      s:longint;

begin

clrscr;

writeln('nhap n:');readln(n);

for i:=1 to n do s:=s*i;

write('tich cua ',n,'so tu nhien dau tien la:',s);

readln;

end.