var n,j,dem:integer;
function ktsnt(a:integer):boolean;
var i,d:integer;
begin
d:=0;
if i=1 then d:=1;
for i:=2 to a div 2 do
if a mod i=0 then d:=d+1;
if d=0 then ktsnt:=true
else ktsnt:=false;
end;
begin
write('n=');readln(n);
j:=0;
dem:=0;
repeat
j:=j+1;
if ktsnt (j) then dem:=dem+1;
until dem=n;
write(' cac so nguyen to dau tien la ',);
readln;
end.