ïÐÒÅÄÅÌÉÔØ äîæ ÆÕÎËÃÉÉ X1->X2
ƒX1ƒX2;
X1ƒX2;
ƒX1ƒX2 X1X2 X1ƒX2;
X1X2 ƒX1ƒX2 ƒX1X2.