function main(arg) {
	arg = arg.split("\n").map(Number)
	var k = arg.pop()
	var data = arg
	for (var i  = 0; i < data.length; i++) {
		for (var j = i + 1; j < data.length; j++) {
			var ans = Math.abs(data[i] - data[j])
			if (ans > k) {
				console.log(':(')
				return
			}
		}
	}
	console.log('Yay!')
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));