int isPrime(int num) {
	if ( num <= 1 ) { return 0; }
	if ( num <= 3 ) { return 1; }
	if ( (num & 0x1) == 0 ) { return 0; }

	int end = sqrt(num);
	for (register int i = 3; i <= end; ++i ) {
		if ( end % i ) return 0;
	}
	return 1;
}

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last modified 2016-04-13 18:03:28