What is the output?

#include

#include

#include

using namespace std;

int main $()$

$\{$

list firstlist, secondlist;

for $($int i $=1$; i $<=2$; i$++)$

$\{$

firstlist.push$\_$back$($i$)$;

secondlist$.$push$\_$back$($i $*10)$;

$\}$

list :: iterator it;

it $=$ firstlist.begin$()$;

copy $($secondlist$.$begin$(),$ secondlist$.$end$(),$ inserter$($firstlist$,$ it$))$;

for $($ it $=$ firstlist.begin$()$; it $!=$ firstlist.end$()$; $++$it $)$

cout $<<*$it $<<""$;

return $0$;

$\}$