thfm

import copy
e,z=enumerate,range
def s(b):
	l=[(x,y)for y,r in e(b)for x,c in e(r)if c==0]
	if len(l)==0:
		return b
	x,y=l[0]
	for g in set(z(1,10))-set(b[y]+[r[x]for r in b]+[c for i in z(y//3*3,y//3*3+3)for c in b[i][x//3*3:x//3*3+3]])-{0}:
		b[y][x]=g
		n=s(copy.deepcopy(b))