symbolic N,M,k;
{ [i,j] -> [] : 0 <= i <= M and 0 <= j <= N and 2i+j = k
                      and not ( exists [i2,j2] :
                              0 <= i2 <= M  and  0 <= j2 <= N
                              and 2i2+j2 = k
                              and i < i2 )                };
{ [i,j] -> [] : 0 <= i <= M and 0 <= j <= N and 2i+j = k
                      and not (  i < M &&  2i-2 <= k &&
				N-k <= 2M
				&& ( N-k < k or N <= 2k && (exists a : k = 2 a)
				))};