An interesting problem on Timus judge

#	User	Rating
1	tourist	3880
2	jiangly	3669
3	ecnerwala	3654
4	Benq	3627
5	orzdevinwang	3612
6	Geothermal	3569
6	cnnfls_csy	3569
8	jqdai0815	3532
9	Radewoosh	3522
10	gyh20	3447

#	User	Contrib.
1	awoo	161
2	maomao90	160
3	adamant	156
4	maroonrk	153
5	atcoder_official	149
6	-is-this-fft-	148
6	SecondThread	148
8	Petr	147
9	nor	144
10	cry	143

Hey, I have found this interesting problem on Timus judge. Here's a link to the problem : 1221. Malevich Strikes Back!. Could you please help me as to how to proceed on this problem.

Thanks in advance.

ameya.loya's blog