我运行的挺快的:
#include <stdio.h>
void main()
{	int k,m,n,i,judge=1,r;
	for(;;)
	{	scanf("%d",&k);
		if(k==0) return;
		m=1;;
		for(;;)
		{	m++;judge=1;r=0;n=2*k
			for(i=0;i<k;i++)
			{	r=(n+m-r)%n;
				if(r>0&&r<=k) {judge=0;break;}
				else { r=(n-r)%n;n--;}
			}
			if(judge) {printf("%d\n",m);break;}
			//printf(" m=%d\n",m);
		}
	}
}