var
a:array[1..100000] of boolean;
n,i:longint;
begin
fillchar(a,sizeof(a),false);
a[2]:=true;
readln(n);
for i:=2 to n do
if a[i] then
begin
writeln(i);
for j:=2 to n div i do a[i*j]:=false;
end;
end.
筛选法找素数.