CVBB ACM Team

long long f(long long x,long long c,long long n)
{
	return ((long long)x*x+c)%n;
}
 
long long PollardRho(long long x)
{
	long long s=0,t=0;
	long long c=rand()%(x-1)+1;
	long long val=1;
	int goal; 
	for(goal=1;;goal<<=1,s=t,val=1)
	{
		int step;
		for(step=1;step<=goal;++step)
		{
			t=f(t,c,x);
			val=val*abs(t-s)%x;
			if((step%127)==0)
			{
				long long d=gcd(val,x);
				if(d>1)
				{
					return d;
				}
			}
		}
		long long d=gcd(val,x);
		if(d>1)
		{
			return d;
		}
	}
}