setInterval(function() {
check()
}, 4000);
var check = function() {
function doCheck(a) {
if (("" + a/a)["length"] !== 1 || a % 20 === 0) {
(function() {}
["constructor"]("debugger")())
} else {
(function() {}
["constructor"]("debugger")())
}
doCheck(++a)
}
try {
doCheck(0)
} catch (err) {}
};
check();