function main(input) {
	var l = input.split("\n");
	var k = l[l.length - 1];
	l.pop();

	var a = "Yay!";
	l.forEach((v, i) => {
		for(var j = i + 1; j < l.length; j ++) {
			if(l[j] - v > k) a = ":(";
		}
	});
	console.log(a);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));